From 3b004e105e1eaa4182213a3606574176a38ca486 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 28 May 2026 09:09:33 +0200
Subject: [PATCH 01/29] feat: set marginal costs for biomass and biogas
 generators

---
 scripts/cba/prepare_rolling_horizon.py | 76 ++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index 8e080f28e6..87bac6530e 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -191,6 +191,79 @@ def apply_msv_to_network(
         n.c[c].dynamic["marginal_cost"].loc[:, s_i] = msv
 
 
+def apply_biomass_biogas_bus_marginal_prices(
+    n,
+    n_msv,
+    carriers=("solid biomass", "biogas"),
+    resample_method="ffill",
+):
+    """
+    Add marginal prices to biomass/biogas generator marginal costs.
+
+    For each biomass/biogas generator in the rolling-horizon network, use the
+    marginal price time series of its attached bus from the MSV network and add it to the generator's base marginal cost.
+
+    effective_marginal_cost_t = static_marginal_cost + bus_marginal_price_t
+
+    Parameters
+    ----------
+    n : pypsa.Network
+        Target network (will be modified in place).
+    n_msv : pypsa.Network
+        Solved MSV network containing bus marginal prices.
+    carriers : tuple[str], optional
+        Generator carriers to apply bus marginal prices to. Defaults to ("solid biomass", "biogas").
+    resample_method : str, optional
+        Method for resampling MSV bus marginal prices to target resolution. Default "ffill".
+    """
+    import pandas as pd
+
+    if n_msv is None or n_msv.buses_t.marginal_price.empty:
+        logger.warning(
+            "No MSV bus marginal prices available; skipping biomass/biogas cost update."
+        )
+        return
+    if isinstance(carriers, str):
+        carriers = (carriers,)
+
+    # Get bus marginal prices from MSV network, resampling if needed
+    msv_mp = n_msv.buses_t.marginal_price
+    if msv_mp.index.equals(n.snapshots):
+        bus_mp = msv_mp
+    else:
+        bus_mp = resample_msv_to_target(msv_mp, n.snapshots, method=resample_method)
+
+    # Get biomass/biogas generators
+    g_idx = n.generators.index[n.generators.carrier.isin(carriers)]
+    if g_idx.empty:
+        logger.info("No biomass/biogas generators found for marginal-price update.")
+        return
+
+    # Ensure marginal cost frame exists on correct index
+    if (
+        n.generators_t.marginal_cost.empty
+        or not n.generators_t.marginal_cost.index.equals(n.snapshots)
+    ):
+        n.generators_t.marginal_cost = pd.DataFrame(index=n.snapshots)
+
+    updated = 0
+    for g in g_idx:
+        bus = n.generators.at[g, "bus"]
+        if bus not in bus_mp.columns:
+            logger.warning(
+                "Skipping %s: bus %s not found in MSV marginal prices.", g, bus
+            )
+            continue
+
+        base_cost = float(n.generators.at[g, "marginal_cost"])
+        n.generators_t.marginal_cost[g] = base_cost + bus_mp[bus].reindex(n.snapshots)
+        updated += 1
+
+    logger.info(
+        "Applied bus-marginal-price costs to %d biomass/biogas generators.", updated
+    )
+
+
 def set_initial_state_from_pf(
     n: pypsa.Network,
     n_msv: pypsa.Network,
@@ -354,6 +427,9 @@ def fix_reservoir_soc_at_boundaries(
     # Apply marginal storage value to all non-cyclic carriers
     apply_msv_to_network(n, n_msv, cyclic_carriers, resample_method)
 
+    # Add bus marginal prices to biomass/biogas generators
+    apply_biomass_biogas_bus_marginal_prices(n, n_msv, resample_method=resample_method)
+
     # Fix reservoir state of charge at window boundaries from perfect foresight
     soc_boundary_carriers = snakemake.params.get("soc_boundary_carriers", [])
     cba_solving = snakemake.config.get("cba", {}).get("solving", {}).get("options", {})

From 20a86c1eec15f56ead8f350d158dc53c17988094 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 28 May 2026 09:13:40 +0200
Subject: [PATCH 02/29] feat: remove volume limits on biomass and biogas
 dispatch

---
 scripts/cba/solve_cba_network.py | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index 78b7d713f5..74f7b114fe 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -158,24 +158,6 @@ def optimize_with_rolling_horizon(
                     n.storage_units_t.state_of_charge.loc[snapshots[start - 1]]
                 )
 
-        # Set per-window energy budgets for volume-limited components
-        # (biomass, biogas) based on PF dispatch stored in generators_t.p
-        for c_name in ["Generator", "Link"]:
-            c = n.c[c_name]
-            if "has_volume_limit" not in c.static.columns:
-                continue
-            vol_idx = c.static.index[c.static["has_volume_limit"] == 1]
-            if vol_idx.empty:
-                continue
-            p_col = "p" if c_name == "Generator" else "p0"
-            pf_p = c.dynamic[p_col]
-            for comp in vol_idx:
-                if comp not in pf_p.columns:
-                    continue
-                window_energy = pf_p.loc[sns, comp].sum()
-                c.static.loc[comp, "e_sum_min"] = window_energy
-                c.static.loc[comp, "e_sum_max"] = window_energy
-
         status, condition = n.optimize(sns, **kwargs)  # type: ignore
         if status != "ok":
             logger.warning(

From 7f2a678df25ec697b1c20469cfc4a4ca53a55716 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 28 May 2026 10:29:39 +0200
Subject: [PATCH 03/29] chore: remove checks and logs

---
 scripts/cba/prepare_rolling_horizon.py | 27 ++++++--------------------
 1 file changed, 6 insertions(+), 21 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index 87bac6530e..e0b2695922 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -216,13 +216,6 @@ def apply_biomass_biogas_bus_marginal_prices(
     resample_method : str, optional
         Method for resampling MSV bus marginal prices to target resolution. Default "ffill".
     """
-    import pandas as pd
-
-    if n_msv is None or n_msv.buses_t.marginal_price.empty:
-        logger.warning(
-            "No MSV bus marginal prices available; skipping biomass/biogas cost update."
-        )
-        return
     if isinstance(carriers, str):
         carriers = (carriers,)
 
@@ -233,34 +226,26 @@ def apply_biomass_biogas_bus_marginal_prices(
     else:
         bus_mp = resample_msv_to_target(msv_mp, n.snapshots, method=resample_method)
 
-    # Get biomass/biogas generators
+    # Get index of generators with target carriers
     g_idx = n.generators.index[n.generators.carrier.isin(carriers)]
-    if g_idx.empty:
-        logger.info("No biomass/biogas generators found for marginal-price update.")
-        return
 
-    # Ensure marginal cost frame exists on correct index
+    # Make sure marginal cost frame exists on correct index
     if (
         n.generators_t.marginal_cost.empty
         or not n.generators_t.marginal_cost.index.equals(n.snapshots)
     ):
         n.generators_t.marginal_cost = pd.DataFrame(index=n.snapshots)
 
-    updated = 0
+    number_updated = 0
     for g in g_idx:
         bus = n.generators.at[g, "bus"]
-        if bus not in bus_mp.columns:
-            logger.warning(
-                "Skipping %s: bus %s not found in MSV marginal prices.", g, bus
-            )
-            continue
-
         base_cost = float(n.generators.at[g, "marginal_cost"])
         n.generators_t.marginal_cost[g] = base_cost + bus_mp[bus].reindex(n.snapshots)
-        updated += 1
+        number_updated += 1
 
     logger.info(
-        "Applied bus-marginal-price costs to %d biomass/biogas generators.", updated
+        "Applied bus-marginal-price costs to %d biomass/biogas generators.",
+        number_updated,
     )
 
 

From 68634be8ebb99440e510bd0c772799b8c6126b97 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Tue, 16 Jun 2026 15:13:26 +0200
Subject: [PATCH 04/29] chore: remove logger and update docs

---
 scripts/cba/prepare_rolling_horizon.py | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index 18552ba4c4..c67d31e0c8 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -200,8 +200,9 @@ def apply_biomass_biogas_bus_marginal_prices(
     """
     Add marginal prices to biomass/biogas generator marginal costs.
 
-    For each biomass/biogas generator in the rolling-horizon network, use the
-    marginal price time series of its attached bus from the MSV network and add it to the generator's base marginal cost.
+    For each biomass/biogas generator in the rolling-horizon network:
+    use the marginal price time series of its attached bus from the MSV network and
+    add the marginal price to the generator's base marginal cost.
 
     effective_marginal_cost_t = static_marginal_cost + bus_marginal_price_t
 
@@ -236,17 +237,10 @@ def apply_biomass_biogas_bus_marginal_prices(
     ):
         n.generators_t.marginal_cost = pd.DataFrame(index=n.snapshots)
 
-    number_updated = 0
     for g in g_idx:
         bus = n.generators.at[g, "bus"]
         base_cost = float(n.generators.at[g, "marginal_cost"])
         n.generators_t.marginal_cost[g] = base_cost + bus_mp[bus].reindex(n.snapshots)
-        number_updated += 1
-
-    logger.info(
-        "Applied bus-marginal-price costs to %d biomass/biogas generators.",
-        number_updated,
-    )
 
 
 def set_initial_state_from_pf(

From d6d711403f48e4872e117d320fea137197b31ccd Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Tue, 16 Jun 2026 15:35:30 +0200
Subject: [PATCH 05/29] refac: make simple refactoring and add comments

---
 scripts/cba/prepare_rolling_horizon.py | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index c67d31e0c8..e89d65ee7a 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -220,15 +220,18 @@ def apply_biomass_biogas_bus_marginal_prices(
     if isinstance(carriers, str):
         carriers = (carriers,)
 
-    # Get bus marginal prices from MSV network, resampling if needed
+    # Get bus marginal prices from MSV network
     msv_mp = n_msv.buses_t.marginal_price
-    if msv_mp.index.equals(n.snapshots):
-        bus_mp = msv_mp
-    else:
-        bus_mp = resample_msv_to_target(msv_mp, n.snapshots, method=resample_method)
+
+    # Resample marginal prices if needed
+    bus_mp = (
+        msv_mp
+        if msv_mp.index.equals(n.snapshots)
+        else resample_msv_to_target(msv_mp, n.snapshots, method=resample_method)
+    )
 
     # Get index of generators with target carriers
-    g_idx = n.generators.index[n.generators.carrier.isin(carriers)]
+    gen_index = n.generators.index[n.generators.carrier.isin(carriers)]
 
     # Make sure marginal cost frame exists on correct index
     if (
@@ -237,7 +240,8 @@ def apply_biomass_biogas_bus_marginal_prices(
     ):
         n.generators_t.marginal_cost = pd.DataFrame(index=n.snapshots)
 
-    for g in g_idx:
+    # Add bus marginal price to generator marginal cost for each generator
+    for g in gen_index:
         bus = n.generators.at[g, "bus"]
         base_cost = float(n.generators.at[g, "marginal_cost"])
         n.generators_t.marginal_cost[g] = base_cost + bus_mp[bus].reindex(n.snapshots)

From 9f233ac18d9133015da744902a31677d4f49eb95 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Tue, 16 Jun 2026 15:36:21 +0200
Subject: [PATCH 06/29] feat: revert `scripts/cba/solve_cba_network.py` back to
 `master`

---
 scripts/cba/solve_cba_network.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index 8d334f98b3..eb21fb57d0 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -158,6 +158,24 @@ def optimize_with_rolling_horizon(
                     n.storage_units_t.state_of_charge.loc[snapshots[start - 1]]
                 )
 
+        # Set per-window energy budgets for volume-limited components
+        # (biomass, biogas) based on PF dispatch stored in generators_t.p
+        for c_name in ["Generator", "Link"]:
+            c = n.c[c_name]
+            if "has_volume_limit" not in c.static.columns:
+                continue
+            vol_idx = c.static.index[c.static["has_volume_limit"] == 1]
+            if vol_idx.empty:
+                continue
+            p_col = "p" if c_name == "Generator" else "p0"
+            pf_p = c.dynamic[p_col]
+            for comp in vol_idx:
+                if comp not in pf_p.columns:
+                    continue
+                window_energy = pf_p.loc[sns, comp].sum()
+                c.static.loc[comp, "e_sum_min"] = window_energy
+                c.static.loc[comp, "e_sum_max"] = window_energy
+
         status, condition = n.optimize(sns, **kwargs)  # type: ignore
         if status != "ok":
             logger.warning(

From d7c28542279c1ad99bdbeab48d45e164b105042f Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Wed, 17 Jun 2026 11:48:34 +0200
Subject: [PATCH 07/29] feat: add slack to biomass/biogas dispatch `e_sum_min`

---
 scripts/cba/solve_cba_network.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index eb21fb57d0..e217ed4002 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -173,7 +173,8 @@ def optimize_with_rolling_horizon(
                 if comp not in pf_p.columns:
                     continue
                 window_energy = pf_p.loc[sns, comp].sum()
-                c.static.loc[comp, "e_sum_min"] = window_energy
+                slack = 0.3
+                c.static.loc[comp, "e_sum_min"] = (1 - slack) * window_energy
                 c.static.loc[comp, "e_sum_max"] = window_energy
 
         status, condition = n.optimize(sns, **kwargs)  # type: ignore

From ea075e4f18ba804af0fcaa416649b31e3e9e624e Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Wed, 17 Jun 2026 12:52:28 +0200
Subject: [PATCH 08/29] feat: increase slack to 40%

---
 scripts/cba/solve_cba_network.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index e217ed4002..dbffa0102a 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -173,7 +173,7 @@ def optimize_with_rolling_horizon(
                 if comp not in pf_p.columns:
                     continue
                 window_energy = pf_p.loc[sns, comp].sum()
-                slack = 0.3
+                slack = 0.4
                 c.static.loc[comp, "e_sum_min"] = (1 - slack) * window_energy
                 c.static.loc[comp, "e_sum_max"] = window_energy
 

From 1977d07d10eae756dbbea8ae09f0164b20935bec Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Wed, 17 Jun 2026 14:33:05 +0200
Subject: [PATCH 09/29] docs: add #719 to doc/release_notes

---
 doc/release_notes.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/doc/release_notes.rst b/doc/release_notes.rst
index 05c2ce4933..83ed7af987 100644
--- a/doc/release_notes.rst
+++ b/doc/release_notes.rst
@@ -33,6 +33,8 @@ Upcoming Open-TYNDP Release
   - Add ``include_objective_constant`` and ``assign_all_duals`` to solving config validator.
   - Add ``gurobi-simplex`` as solver option.
 
+* Change dispatch of biomass and biogas generators in CBA by (a) adding marginal prices of buses to the generators' marginal costs and (b) including a slack of 40% in the `e_sum_min` (https://github.com/open-energy-transition/open-tyndp/pull/719). 
+
 **Bugfixes and Compatibility**
 
 **Documentation**

From 0698bd424e092af2b8eb15f13d0fe0b8b7928cf2 Mon Sep 17 00:00:00 2001
From: meas <measrainsey@pm.me>
Date: Thu, 2 Jul 2026 17:22:52 +0200
Subject: [PATCH 10/29] refac: use `n_msv.snapshots` instead of `msv_mp.index`

Co-authored-by: Thomas Gilon <thomas.gilon@openenergytransition.org>
---
 scripts/cba/prepare_rolling_horizon.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index e89d65ee7a..6e2ae39914 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -226,7 +226,7 @@ def apply_biomass_biogas_bus_marginal_prices(
     # Resample marginal prices if needed
     bus_mp = (
         msv_mp
-        if msv_mp.index.equals(n.snapshots)
+        if n_msv.snapshots.equals(n.snapshots)
         else resample_msv_to_target(msv_mp, n.snapshots, method=resample_method)
     )
 

From 9dc4fee6b3d195b9b0c15860e6042bfac559bff2 Mon Sep 17 00:00:00 2001
From: meas <measrainsey@pm.me>
Date: Thu, 2 Jul 2026 17:23:47 +0200
Subject: [PATCH 11/29] feat: directly set marginal price as marginal cost,
 instead of adding

Co-authored-by: Thomas Gilon <thomas.gilon@openenergytransition.org>
---
 scripts/cba/prepare_rolling_horizon.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index 6e2ae39914..ebac8558a3 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -243,8 +243,7 @@ def apply_biomass_biogas_bus_marginal_prices(
     # Add bus marginal price to generator marginal cost for each generator
     for g in gen_index:
         bus = n.generators.at[g, "bus"]
-        base_cost = float(n.generators.at[g, "marginal_cost"])
-        n.generators_t.marginal_cost[g] = base_cost + bus_mp[bus].reindex(n.snapshots)
+        n.generators_t.marginal_cost[g] = bus_mp[bus].reindex(n.snapshots)
 
 
 def set_initial_state_from_pf(

From be81501adb7c21d96ae697424e4a2344c2bc1846 Mon Sep 17 00:00:00 2001
From: meas <measrainsey@pm.me>
Date: Thu, 2 Jul 2026 17:24:04 +0200
Subject: [PATCH 12/29] chore: edit comment

Co-authored-by: Thomas Gilon <thomas.gilon@openenergytransition.org>
---
 scripts/cba/prepare_rolling_horizon.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index ebac8558a3..95ea21f135 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -409,7 +409,7 @@ def fix_reservoir_soc_at_boundaries(
     # Apply marginal storage value to all non-cyclic carriers
     apply_msv_to_network(n, n_msv, cyclic_carriers, resample_method)
 
-    # Add bus marginal prices to biomass/biogas generators
+    # Add bus marginal prices to the marginal costs of the biomass/biogas generators
     apply_biomass_biogas_bus_marginal_prices(n, n_msv, resample_method=resample_method)
 
     # Fix reservoir state of charge at window boundaries from perfect foresight

From ee16ef4d2c107bfd12516edc578e0d797fdf28ff Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 2 Jul 2026 22:18:51 +0200
Subject: [PATCH 13/29] feat: create config option `cba.biomass_biogas_slack`
 for slack instead of hardcoding

---
 config/config.default.yaml           |  1 +
 config/config.tyndp.yaml             |  1 +
 config/schema.default.json           | 14 ++++++++++++++
 config/test/config.cyears.yaml       |  1 +
 config/test/config.tyndp.yaml        |  1 +
 scripts/cba/solve_cba_network.py     |  6 ++++--
 scripts/lib/validation/config/cba.py |  6 ++++++
 7 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/config/config.default.yaml b/config/config.default.yaml
index 3ef15b3843..5f6bbaa54f 100644
--- a/config/config.default.yaml
+++ b/config/config.default.yaml
@@ -1604,6 +1604,7 @@ cba:
   area: tyndp
   remove_noisy_costs: true
   negative_toot_capacity: zero
+  biomass_biogas_slack: 0.4
   storage:
     cyclic_carriers:
     - battery
diff --git a/config/config.tyndp.yaml b/config/config.tyndp.yaml
index 4f0b59a88c..f61206ad05 100644
--- a/config/config.tyndp.yaml
+++ b/config/config.tyndp.yaml
@@ -433,6 +433,7 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
+  biomass_biogas_slack: 0.4 # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
 
   # Storage settings for dispatch
   storage:
diff --git a/config/schema.default.json b/config/schema.default.json
index 82119850e0..bc980d3039 100644
--- a/config/schema.default.json
+++ b/config/schema.default.json
@@ -533,6 +533,13 @@
           ],
           "type": "string"
         },
+        "biomass_biogas_slack": {
+          "default": 0.4,
+          "description": "Slack applied to rolling-horizon biomass and biogas `e_sum_min` limits as a fraction of the perfect-foresight window dispatch.",
+          "maximum": 1.0,
+          "minimum": 0.0,
+          "type": "number"
+        },
         "storage": {
           "description": "Configuration for `cba.storage` settings.",
           "properties": {
@@ -15468,6 +15475,13 @@
           ],
           "type": "string"
         },
+        "biomass_biogas_slack": {
+          "default": 0.4,
+          "description": "Slack applied to rolling-horizon biomass and biogas `e_sum_min` limits as a fraction of the perfect-foresight window dispatch.",
+          "maximum": 1.0,
+          "minimum": 0.0,
+          "type": "number"
+        },
         "storage": {
           "description": "Configuration for `cba.storage` settings.",
           "properties": {
diff --git a/config/test/config.cyears.yaml b/config/test/config.cyears.yaml
index 25d80bd3ed..e33d6484ea 100644
--- a/config/test/config.cyears.yaml
+++ b/config/test/config.cyears.yaml
@@ -443,6 +443,7 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
+  biomass_biogas_slack: 0.4 # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
 
   # Storage settings for dispatch
   storage:
diff --git a/config/test/config.tyndp.yaml b/config/test/config.tyndp.yaml
index bbd7f94531..eaa0d0d186 100644
--- a/config/test/config.tyndp.yaml
+++ b/config/test/config.tyndp.yaml
@@ -441,6 +441,7 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
+  biomass_biogas_slack: 0.4 # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
 
   # Storage settings for dispatch
   storage:
diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index dbffa0102a..057d611db5 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -136,6 +136,7 @@ def optimize_with_rolling_horizon(
     assert len(snapshots), "Need at least one snapshot to optimize"
 
     fallback_solver = kwargs.pop("fallback_solver", None)
+    biomass_biogas_slack = n.config["cba"].get("biomass_biogas_slack", 0.4)
 
     starting_points = range(0, len(snapshots), horizon - overlap)
     for i, start in tqdm(enumerate(starting_points), total=len(starting_points)):
@@ -173,8 +174,9 @@ def optimize_with_rolling_horizon(
                 if comp not in pf_p.columns:
                     continue
                 window_energy = pf_p.loc[sns, comp].sum()
-                slack = 0.4
-                c.static.loc[comp, "e_sum_min"] = (1 - slack) * window_energy
+                c.static.loc[comp, "e_sum_min"] = (
+                    1 - biomass_biogas_slack
+                ) * window_energy
                 c.static.loc[comp, "e_sum_max"] = window_energy
 
         status, condition = n.optimize(sns, **kwargs)  # type: ignore
diff --git a/scripts/lib/validation/config/cba.py b/scripts/lib/validation/config/cba.py
index 5ee591f876..7fac2a88cb 100644
--- a/scripts/lib/validation/config/cba.py
+++ b/scripts/lib/validation/config/cba.py
@@ -177,6 +177,12 @@ class CbaConfig(BaseModel):
         default="zero",
         description="How to handle TOOT project removal when removing project capacity would make an existing interconnector capacity negative. 'zero' clamps the resulting capacity to zero and continues; 'break' raises an error.",
     )
+    biomass_biogas_slack: float = Field(
+        0.4,
+        ge=0.0,
+        le=1.0,
+        description="Slack applied to rolling-horizon biomass and biogas `e_sum_min` limits as a fraction of the perfect-foresight window dispatch.",
+    )
     storage: _CbaStorageConfig = Field(
         default_factory=_CbaStorageConfig,
         description="Storage configuration for the cost-benefit analysis workflow.",

From ab0f708df3b4a1e34c3b9977d63d34f0664843fe Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Fri, 3 Jul 2026 08:38:32 +0200
Subject: [PATCH 14/29] refac: filter by both carriers and volume limits

---
 scripts/cba/solve_cba_network.py | 45 +++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index 057d611db5..fbecda2941 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -51,6 +51,37 @@
 logger = logging.getLogger(__name__)
 
 
+def get_components_with_volume_limits(
+    n: pypsa.Network,
+    type: str,
+    carriers: list[str],
+) -> pd.Index:
+    """
+    Return components that have volume limits, given a list of carriers.
+
+    Parameters
+    ----------
+    n : pypsa.Network
+        PyPSA network
+    type : str
+        Component type, e.g. "Generator" or "Link"
+    carriers : list of str
+        List of carriers to filter components by
+
+    Returns
+    -------
+    pd.Index
+        Index of components that have volume limits and match the given carriers
+    """
+    static = n.c[type].static
+    if "has_volume_limit" not in static.columns:
+        return pd.Index([])
+
+    return static.index[
+        static["carrier"].isin(carriers) & static["has_volume_limit"].eq(1)
+    ]
+
+
 def extra_functionality(
     n: pypsa.Network,
     snapshots: pd.DatetimeIndex,
@@ -159,13 +190,13 @@ def optimize_with_rolling_horizon(
                     n.storage_units_t.state_of_charge.loc[snapshots[start - 1]]
                 )
 
-        # Set per-window energy budgets for volume-limited components
-        # (biomass, biogas) based on PF dispatch stored in generators_t.p
-        for c_name in ["Generator", "Link"]:
+        # Set per-window energy budgets for biomass/biogas components
+        # based on PF dispatch stored in generators_t.p
+        for c_name in ["Link"]:
             c = n.c[c_name]
-            if "has_volume_limit" not in c.static.columns:
-                continue
-            vol_idx = c.static.index[c.static["has_volume_limit"] == 1]
+            vol_idx = get_components_with_volume_limits(
+                n, c_name, ["solid biomass", "biogas"]
+            )
             if vol_idx.empty:
                 continue
             p_col = "p" if c_name == "Generator" else "p0"
@@ -305,7 +336,7 @@ def solve_network(
         snakemake = mock_snakemake(
             "solve_cba_network",
             run="NT",
-            cba_project="t4",
+            cba_project="t16",
             planning_horizons="2030",
             configfiles=["config/config.tyndp.yaml"],
         )

From 622132e9e69523bc79442349bfd9e710f364f017 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Fri, 3 Jul 2026 09:00:46 +0200
Subject: [PATCH 15/29] refac: remove setting marginal cost dataframe

---
 scripts/cba/prepare_rolling_horizon.py | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index 95ea21f135..231d6bd84a 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -233,14 +233,6 @@ def apply_biomass_biogas_bus_marginal_prices(
     # Get index of generators with target carriers
     gen_index = n.generators.index[n.generators.carrier.isin(carriers)]
 
-    # Make sure marginal cost frame exists on correct index
-    if (
-        n.generators_t.marginal_cost.empty
-        or not n.generators_t.marginal_cost.index.equals(n.snapshots)
-    ):
-        n.generators_t.marginal_cost = pd.DataFrame(index=n.snapshots)
-
-    # Add bus marginal price to generator marginal cost for each generator
     for g in gen_index:
         bus = n.generators.at[g, "bus"]
         n.generators_t.marginal_cost[g] = bus_mp[bus].reindex(n.snapshots)

From dde4f58974430b805b25657dd981041079b9f141 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Fri, 3 Jul 2026 09:04:34 +0200
Subject: [PATCH 16/29] chore: add type hints

---
 scripts/cba/prepare_rolling_horizon.py | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index 231d6bd84a..1dd3167622 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -192,10 +192,10 @@ def apply_msv_to_network(
 
 
 def apply_biomass_biogas_bus_marginal_prices(
-    n,
-    n_msv,
-    carriers=("solid biomass", "biogas"),
-    resample_method="ffill",
+    n: pypsa.Network,
+    n_msv: pypsa.Network,
+    carriers: list[str] = ["solid biomass", "biogas"],
+    resample_method: str = "ffill",
 ):
     """
     Add marginal prices to biomass/biogas generator marginal costs.
@@ -212,13 +212,13 @@ def apply_biomass_biogas_bus_marginal_prices(
         Target network (will be modified in place).
     n_msv : pypsa.Network
         Solved MSV network containing bus marginal prices.
-    carriers : tuple[str], optional
-        Generator carriers to apply bus marginal prices to. Defaults to ("solid biomass", "biogas").
+    carriers : list[str], optional
+        Generator carriers to apply bus marginal prices to. Defaults to ["solid biomass", "biogas"].
     resample_method : str, optional
         Method for resampling MSV bus marginal prices to target resolution. Default "ffill".
     """
     if isinstance(carriers, str):
-        carriers = (carriers,)
+        carriers = [carriers]
 
     # Get bus marginal prices from MSV network
     msv_mp = n_msv.buses_t.marginal_price
@@ -233,6 +233,7 @@ def apply_biomass_biogas_bus_marginal_prices(
     # Get index of generators with target carriers
     gen_index = n.generators.index[n.generators.carrier.isin(carriers)]
 
+    # Set marginal cost for each generator based on the marginal price of its bus
     for g in gen_index:
         bus = n.generators.at[g, "bus"]
         n.generators_t.marginal_cost[g] = bus_mp[bus].reindex(n.snapshots)

From ca262db50bdcd27da8b09f9da9a90e662dc60b3c Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Fri, 3 Jul 2026 12:15:00 +0200
Subject: [PATCH 17/29] feat: add `cba.biomass_biogas_slack` config option as
 rule input

---
 rules/cba.smk | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/rules/cba.smk b/rules/cba.smk
index 7baf9ab965..578789cce6 100644
--- a/rules/cba.smk
+++ b/rules/cba.smk
@@ -387,6 +387,7 @@ rule solve_cba_reference_network:
     params:
         solving=config_provider("solving"),
         cba_solving=config_provider("cba", "solving"),
+        biomass_biogas_slack=config_provider("cba", "biomass_biogas_slack"),
         foresight=config_provider("foresight"),
         time_resolution=config_provider("clustering", "temporal", "resolution_sector"),
         custom_extra_functionality=None,
@@ -408,6 +409,7 @@ rule solve_cba_network:
     params:
         solving=config_provider("solving"),
         cba_solving=config_provider("cba", "solving"),
+        biomass_biogas_slack=config_provider("cba", "biomass_biogas_slack"),
         foresight=config_provider("foresight"),
         time_resolution=config_provider("clustering", "temporal", "resolution_sector"),
         custom_extra_functionality=None,

From e5195a787f0a4705186cb8f35da9e2fbf55efd91 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Fri, 3 Jul 2026 17:26:34 +0200
Subject: [PATCH 18/29] fix: add back Generator type

---
 scripts/cba/solve_cba_network.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index fbecda2941..5d712f5c36 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -192,7 +192,7 @@ def optimize_with_rolling_horizon(
 
         # Set per-window energy budgets for biomass/biogas components
         # based on PF dispatch stored in generators_t.p
-        for c_name in ["Link"]:
+        for c_name in ["Generator", "Link"]:
             c = n.c[c_name]
             vol_idx = get_components_with_volume_limits(
                 n, c_name, ["solid biomass", "biogas"]

From ea3aa4ee7db6ee0bcd81fcf8bbb88e9c49625daf Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Mon, 6 Jul 2026 15:27:45 +0200
Subject: [PATCH 19/29] docs: add #719 to doc/release_notes

---
 doc/release_notes.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/doc/release_notes.md b/doc/release_notes.md
index 79c6bf77cc..574ffcb53a 100644
--- a/doc/release_notes.md
+++ b/doc/release_notes.md
@@ -29,6 +29,8 @@
     - Add `include_objective_constant` and `assign_all_duals` to solving config validator.
     - Add `gurobi-simplex` as solver option.
 
+* Change dispatch of biomass and biogas generators in CBA by (a) setting the buses' marginal prices as the generators' marginal costs and (b) including a slack of 40% in the `e_sum_min` (https://github.com/open-energy-transition/open-tyndp/pull/719). 
+
 **Bugfixes and Compatibility**
 
 **Documentation**

From ecbd8032f1ebbfd74f5777a173ac126f6b70c139 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 6 Jul 2026 13:28:11 +0000
Subject: [PATCH 20/29] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 rules/cba.smk | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/rules/cba.smk b/rules/cba.smk
index 4cbf7c263b..7b4039d0a7 100644
--- a/rules/cba.smk
+++ b/rules/cba.smk
@@ -384,13 +384,6 @@ rule prepare_project:
 
 # Solve reference network with rolling horizon (MSV already applied)
 rule solve_cba_reference_network:
-    params:
-        solving=config_provider("solving"),
-        cba_solving=config_provider("cba", "solving"),
-        biomass_biogas_slack=config_provider("cba", "biomass_biogas_slack"),
-        foresight=config_provider("foresight"),
-        time_resolution=config_provider("clustering", "temporal", "resolution_sector"),
-        custom_extra_functionality=None,
     input:
         network=rules.prepare_rolling_horizon.output.network,
     output:

From 5532a4facbdb209bdfe03a0f73e9a081e9c99df2 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Mon, 6 Jul 2026 15:39:00 +0200
Subject: [PATCH 21/29] chore: add details in comments of configs

---
 config/config.tyndp.yaml             | 4 +++-
 config/schema.default.json           | 4 ++--
 config/test/config.cyears.yaml       | 4 +++-
 scripts/lib/validation/config/cba.py | 2 +-
 4 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/config/config.tyndp.yaml b/config/config.tyndp.yaml
index 07507cc960..9aa0d42d13 100644
--- a/config/config.tyndp.yaml
+++ b/config/config.tyndp.yaml
@@ -433,7 +433,9 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
-  biomass_biogas_slack: 0.4 # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
+  # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
+  # Set to 40% to allow for all projects to successfully solve in 1H resolution
+  biomass_biogas_slack: 0.4
 
   # Storage settings for dispatch
   storage:
diff --git a/config/schema.default.json b/config/schema.default.json
index 74e57a1b93..8dd2484fe7 100644
--- a/config/schema.default.json
+++ b/config/schema.default.json
@@ -540,7 +540,7 @@
         },
         "biomass_biogas_slack": {
           "default": 0.4,
-          "description": "Slack applied to rolling-horizon biomass and biogas `e_sum_min` limits as a fraction of the perfect-foresight window dispatch.",
+          "description": "Slack applied to CBA rolling horizon biomass and biogas `e_sum_min` limits. The slack is applied as a fraction of the original value, allowing for more flexible dispatch of biomass and biogas units in the CBA workflow. This is only applied to the `e_sum_min`, while the `e_sum_max` remains unchanged.",
           "maximum": 1.0,
           "minimum": 0.0,
           "type": "number"
@@ -15700,7 +15700,7 @@
         },
         "biomass_biogas_slack": {
           "default": 0.4,
-          "description": "Slack applied to rolling-horizon biomass and biogas `e_sum_min` limits as a fraction of the perfect-foresight window dispatch.",
+          "description": "Slack applied to CBA rolling horizon biomass and biogas `e_sum_min` limits. The slack is applied as a fraction of the original value, allowing for more flexible dispatch of biomass and biogas units in the CBA workflow. This is only applied to the `e_sum_min`, while the `e_sum_max` remains unchanged.",
           "maximum": 1.0,
           "minimum": 0.0,
           "type": "number"
diff --git a/config/test/config.cyears.yaml b/config/test/config.cyears.yaml
index 84ce71690c..1ac92b54da 100644
--- a/config/test/config.cyears.yaml
+++ b/config/test/config.cyears.yaml
@@ -443,7 +443,9 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
-  biomass_biogas_slack: 0.4 # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
+  # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
+  # Set to 40% to allow for all projects to successfully solve in 1H resolution
+  biomass_biogas_slack: 0.4
 
   # Storage settings for dispatch
   storage:
diff --git a/scripts/lib/validation/config/cba.py b/scripts/lib/validation/config/cba.py
index 7fac2a88cb..ec8b8dab14 100644
--- a/scripts/lib/validation/config/cba.py
+++ b/scripts/lib/validation/config/cba.py
@@ -181,7 +181,7 @@ class CbaConfig(BaseModel):
         0.4,
         ge=0.0,
         le=1.0,
-        description="Slack applied to rolling-horizon biomass and biogas `e_sum_min` limits as a fraction of the perfect-foresight window dispatch.",
+        description="Slack applied to CBA rolling horizon biomass and biogas `e_sum_min` limits. The slack is applied as a fraction of the original value, allowing for more flexible dispatch of biomass and biogas units in the CBA workflow. This is only applied to the `e_sum_min`, while the `e_sum_max` remains unchanged.",
     )
     storage: _CbaStorageConfig = Field(
         default_factory=_CbaStorageConfig,

From 34f15ec2a73aed74eb4d747fd45775d94ad6d695 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Mon, 6 Jul 2026 15:41:37 +0200
Subject: [PATCH 22/29] docs: change function description

---
 scripts/cba/prepare_rolling_horizon.py | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index 1dd3167622..d458f53698 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -198,18 +198,16 @@ def apply_biomass_biogas_bus_marginal_prices(
     resample_method: str = "ffill",
 ):
     """
-    Add marginal prices to biomass/biogas generator marginal costs.
+    Set biomass/biogas buses' marginal prices as the generators' marginal costs.
 
-    For each biomass/biogas generator in the rolling-horizon network:
+    For each biomass/biogas generator in the rolling horizon network:
     use the marginal price time series of its attached bus from the MSV network and
-    add the marginal price to the generator's base marginal cost.
-
-    effective_marginal_cost_t = static_marginal_cost + bus_marginal_price_t
+    set the marginal price as the generator's marginal cost.
 
     Parameters
     ----------
     n : pypsa.Network
-        Target network (will be modified in place).
+        Target network.
     n_msv : pypsa.Network
         Solved MSV network containing bus marginal prices.
     carriers : list[str], optional

From 4e0abee5937f50e7650404c3e81e90177150362f Mon Sep 17 00:00:00 2001
From: meas <measrainsey@pm.me>
Date: Wed, 8 Jul 2026 10:02:43 +0200
Subject: [PATCH 23/29] chore: edit comment for slack in
 config/test/config.tyndp.yaml

Co-authored-by: Thomas Gilon <thomas.gilon@openenergytransition.org>
---
 config/test/config.tyndp.yaml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/config/test/config.tyndp.yaml b/config/test/config.tyndp.yaml
index e664ba2c5e..3819407a9d 100644
--- a/config/test/config.tyndp.yaml
+++ b/config/test/config.tyndp.yaml
@@ -441,7 +441,9 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
-  biomass_biogas_slack: 0.4 # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
+  # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
+  # Set to 40% to allow for all projects to successfully solve in 1H resolution
+  biomass_biogas_slack: 0.4
 
   # Storage settings for dispatch
   storage:

From 41b387e375be02f88a3172293720bc0075f12289 Mon Sep 17 00:00:00 2001
From: meas <measrainsey@pm.me>
Date: Wed, 8 Jul 2026 10:03:04 +0200
Subject: [PATCH 24/29] doc: edit link in PR description

Co-authored-by: Thomas Gilon <thomas.gilon@openenergytransition.org>
---
 doc/release_notes.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/release_notes.md b/doc/release_notes.md
index 574ffcb53a..3db6ddd202 100644
--- a/doc/release_notes.md
+++ b/doc/release_notes.md
@@ -29,7 +29,7 @@
     - Add `include_objective_constant` and `assign_all_duals` to solving config validator.
     - Add `gurobi-simplex` as solver option.
 
-* Change dispatch of biomass and biogas generators in CBA by (a) setting the buses' marginal prices as the generators' marginal costs and (b) including a slack of 40% in the `e_sum_min` (https://github.com/open-energy-transition/open-tyndp/pull/719). 
+* Change dispatch of biomass and biogas generators in CBA by (a) setting the buses' marginal prices as the generators' marginal costs and (b) including a slack of 40% in the `e_sum_min` ([#719](https://github.com/open-energy-transition/open-tyndp/pull/719)). 
 
 **Bugfixes and Compatibility**
 

From cb0a84f43d49cb98c21cfba2bd72cfad9f2fcceb Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Wed, 8 Jul 2026 10:35:45 +0200
Subject: [PATCH 25/29] refac: change `has_volume_limit` to bool

---
 scripts/cba/prepare_rolling_horizon.py | 4 ++--
 scripts/cba/solve_cba_network.py       | 4 +---
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/scripts/cba/prepare_rolling_horizon.py b/scripts/cba/prepare_rolling_horizon.py
index d458f53698..48659efa1c 100644
--- a/scripts/cba/prepare_rolling_horizon.py
+++ b/scripts/cba/prepare_rolling_horizon.py
@@ -130,8 +130,8 @@ def disable_volume_limits(n: pypsa.Network):
     for c in n.components[{"Generator", "Link"}]:
         has_e_sum_min = isfinite(c.static.get("e_sum_min", []))
         if has_e_sum_min.any():
-            c.static["has_volume_limit"] = 0
-            c.static.loc[has_e_sum_min, "has_volume_limit"] = 1
+            c.static["has_volume_limit"] = False
+            c.static.loc[has_e_sum_min, "has_volume_limit"] = True
             c.static.loc[has_e_sum_min, "e_sum_min"] = -inf
             c.static.loc[has_e_sum_min, "e_sum_max"] = inf
 
diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index 5d712f5c36..c28433910d 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -77,9 +77,7 @@ def get_components_with_volume_limits(
     if "has_volume_limit" not in static.columns:
         return pd.Index([])
 
-    return static.index[
-        static["carrier"].isin(carriers) & static["has_volume_limit"].eq(1)
-    ]
+    return static.index[static["carrier"].isin(carriers) & static["has_volume_limit"]]
 
 
 def extra_functionality(

From 7a6d7af2d2672f01b4f280af18df8c10490d454e Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 9 Jul 2026 19:43:55 +0200
Subject: [PATCH 26/29] feat: remove `e_sum` energy budget constraint on
 biomass/biogas slack

---
 scripts/cba/solve_cba_network.py | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index dc93c60f29..5469826dab 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -221,26 +221,6 @@ def optimize_with_rolling_horizon(
                     n.storage_units_t.state_of_charge.loc[snapshots[start - 1]]
                 )
 
-        # Set per-window energy budgets for biomass/biogas components
-        # based on PF dispatch stored in generators_t.p
-        for c_name in ["Generator", "Link"]:
-            c = n.c[c_name]
-            vol_idx = get_components_with_volume_limits(
-                n, c_name, ["solid biomass", "biogas"]
-            )
-            if vol_idx.empty:
-                continue
-            p_col = "p" if c_name == "Generator" else "p0"
-            pf_p = c.dynamic[p_col]
-            for comp in vol_idx:
-                if comp not in pf_p.columns:
-                    continue
-                window_energy = pf_p.loc[sns, comp].sum()
-                c.static.loc[comp, "e_sum_min"] = (
-                    1 - biomass_biogas_slack
-                ) * window_energy
-                c.static.loc[comp, "e_sum_max"] = window_energy
-
         status, condition = n.optimize(sns, **kwargs)  # type: ignore
 
         # If solve is successful, dispose of Model object to release license before next rolling horizon

From 29e7e87dced5a234ffa34b575c1e426cda2a6547 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 9 Jul 2026 19:52:23 +0200
Subject: [PATCH 27/29] feat: remove `cba.biomass_biogas_slack` config option

---
 config/config.default.yaml           |  1 -
 config/config.tyndp.yaml             |  3 ---
 config/schema.default.json           | 14 --------------
 config/test/config.cyears.yaml       |  3 ---
 config/test/config.tyndp.yaml        |  3 ---
 rules/cba.smk                        |  1 -
 scripts/cba/solve_cba_network.py     |  1 -
 scripts/lib/validation/config/cba.py |  6 ------
 8 files changed, 32 deletions(-)

diff --git a/config/config.default.yaml b/config/config.default.yaml
index aa6b221ffd..b616b54f8c 100644
--- a/config/config.default.yaml
+++ b/config/config.default.yaml
@@ -1617,7 +1617,6 @@ cba:
   area: tyndp
   remove_noisy_costs: true
   negative_toot_capacity: zero
-  biomass_biogas_slack: 0.4
   storage:
     cyclic_carriers:
     - battery
diff --git a/config/config.tyndp.yaml b/config/config.tyndp.yaml
index 9aa0d42d13..f6e1351f45 100644
--- a/config/config.tyndp.yaml
+++ b/config/config.tyndp.yaml
@@ -433,9 +433,6 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
-  # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
-  # Set to 40% to allow for all projects to successfully solve in 1H resolution
-  biomass_biogas_slack: 0.4
 
   # Storage settings for dispatch
   storage:
diff --git a/config/schema.default.json b/config/schema.default.json
index 8dd2484fe7..fd78387fa1 100644
--- a/config/schema.default.json
+++ b/config/schema.default.json
@@ -538,13 +538,6 @@
           ],
           "type": "string"
         },
-        "biomass_biogas_slack": {
-          "default": 0.4,
-          "description": "Slack applied to CBA rolling horizon biomass and biogas `e_sum_min` limits. The slack is applied as a fraction of the original value, allowing for more flexible dispatch of biomass and biogas units in the CBA workflow. This is only applied to the `e_sum_min`, while the `e_sum_max` remains unchanged.",
-          "maximum": 1.0,
-          "minimum": 0.0,
-          "type": "number"
-        },
         "storage": {
           "description": "Configuration for `cba.storage` settings.",
           "properties": {
@@ -15698,13 +15691,6 @@
           ],
           "type": "string"
         },
-        "biomass_biogas_slack": {
-          "default": 0.4,
-          "description": "Slack applied to CBA rolling horizon biomass and biogas `e_sum_min` limits. The slack is applied as a fraction of the original value, allowing for more flexible dispatch of biomass and biogas units in the CBA workflow. This is only applied to the `e_sum_min`, while the `e_sum_max` remains unchanged.",
-          "maximum": 1.0,
-          "minimum": 0.0,
-          "type": "number"
-        },
         "storage": {
           "description": "Configuration for `cba.storage` settings.",
           "properties": {
diff --git a/config/test/config.cyears.yaml b/config/test/config.cyears.yaml
index 1ac92b54da..2981f59e1e 100644
--- a/config/test/config.cyears.yaml
+++ b/config/test/config.cyears.yaml
@@ -443,9 +443,6 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
-  # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
-  # Set to 40% to allow for all projects to successfully solve in 1H resolution
-  biomass_biogas_slack: 0.4
 
   # Storage settings for dispatch
   storage:
diff --git a/config/test/config.tyndp.yaml b/config/test/config.tyndp.yaml
index 3819407a9d..55d6383728 100644
--- a/config/test/config.tyndp.yaml
+++ b/config/test/config.tyndp.yaml
@@ -441,9 +441,6 @@ cba:
   area: tyndp # options: tyndp (TODO: entso-e, eu27)
   remove_noisy_costs: true # Use pre-noise costs for indicators while keeping noisy costs in the solve
   negative_toot_capacity: zero
-  # Slack on rolling-horizon biomass and biogas e_sum_min volume limits
-  # Set to 40% to allow for all projects to successfully solve in 1H resolution
-  biomass_biogas_slack: 0.4
 
   # Storage settings for dispatch
   storage:
diff --git a/rules/cba.smk b/rules/cba.smk
index 7b4039d0a7..c90db6d1f6 100644
--- a/rules/cba.smk
+++ b/rules/cba.smk
@@ -396,7 +396,6 @@ rule solve_cba_reference_network:
     params:
         solving=config_provider("solving"),
         cba_solving=config_provider("cba", "solving"),
-        biomass_biogas_slack=config_provider("cba", "biomass_biogas_slack"),
         foresight=config_provider("foresight"),
         time_resolution=config_provider("clustering", "temporal", "resolution_sector"),
         custom_extra_functionality=None,
diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index 5469826dab..e252680503 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -198,7 +198,6 @@ def optimize_with_rolling_horizon(
     assert len(snapshots), "Need at least one snapshot to optimize"
 
     fallback_solver = kwargs.pop("fallback_solver", None)
-    biomass_biogas_slack = n.config["cba"].get("biomass_biogas_slack", 0.4)
 
     starting_points = range(0, len(snapshots), horizon - overlap)
     for i, start in tqdm(enumerate(starting_points), total=len(starting_points)):
diff --git a/scripts/lib/validation/config/cba.py b/scripts/lib/validation/config/cba.py
index ec8b8dab14..5ee591f876 100644
--- a/scripts/lib/validation/config/cba.py
+++ b/scripts/lib/validation/config/cba.py
@@ -177,12 +177,6 @@ class CbaConfig(BaseModel):
         default="zero",
         description="How to handle TOOT project removal when removing project capacity would make an existing interconnector capacity negative. 'zero' clamps the resulting capacity to zero and continues; 'break' raises an error.",
     )
-    biomass_biogas_slack: float = Field(
-        0.4,
-        ge=0.0,
-        le=1.0,
-        description="Slack applied to CBA rolling horizon biomass and biogas `e_sum_min` limits. The slack is applied as a fraction of the original value, allowing for more flexible dispatch of biomass and biogas units in the CBA workflow. This is only applied to the `e_sum_min`, while the `e_sum_max` remains unchanged.",
-    )
     storage: _CbaStorageConfig = Field(
         default_factory=_CbaStorageConfig,
         description="Storage configuration for the cost-benefit analysis workflow.",

From 4930a70f0a71faefa7d77e4016c4da6502412673 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 9 Jul 2026 19:54:35 +0200
Subject: [PATCH 28/29] refac: remove `get_components_with_volume_limits()`
 function

---
 scripts/cba/solve_cba_network.py | 29 -----------------------------
 1 file changed, 29 deletions(-)

diff --git a/scripts/cba/solve_cba_network.py b/scripts/cba/solve_cba_network.py
index e252680503..781dcefe42 100644
--- a/scripts/cba/solve_cba_network.py
+++ b/scripts/cba/solve_cba_network.py
@@ -51,35 +51,6 @@
 logger = logging.getLogger(__name__)
 
 
-def get_components_with_volume_limits(
-    n: pypsa.Network,
-    type: str,
-    carriers: list[str],
-) -> pd.Index:
-    """
-    Return components that have volume limits, given a list of carriers.
-
-    Parameters
-    ----------
-    n : pypsa.Network
-        PyPSA network
-    type : str
-        Component type, e.g. "Generator" or "Link"
-    carriers : list of str
-        List of carriers to filter components by
-
-    Returns
-    -------
-    pd.Index
-        Index of components that have volume limits and match the given carriers
-    """
-    static = n.c[type].static
-    if "has_volume_limit" not in static.columns:
-        return pd.Index([])
-
-    return static.index[static["carrier"].isin(carriers) & static["has_volume_limit"]]
-
-
 def dispose_model(n: pypsa.Network) -> None:
     """
     Explicitly dispose of Model object.

From 7cf340dade0d2cb0a3c5a7936c3a64d5bcb41c79 Mon Sep 17 00:00:00 2001
From: Measrainsey Meng <measrainsey@pm.me>
Date: Thu, 9 Jul 2026 19:56:40 +0200
Subject: [PATCH 29/29] docs: edit PR description in doc/release_notes

---
 doc/release_notes.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/release_notes.md b/doc/release_notes.md
index b8bfb4c97e..00cc3c3131 100644
--- a/doc/release_notes.md
+++ b/doc/release_notes.md
@@ -29,7 +29,7 @@
     - Add `include_objective_constant` and `assign_all_duals` to solving config validator.
     - Add `gurobi-simplex` as solver option.
 
-* Change dispatch of biomass and biogas generators in CBA by (a) setting the buses' marginal prices as the generators' marginal costs and (b) including a slack of 40% in the `e_sum_min` ([#719](https://github.com/open-energy-transition/open-tyndp/pull/719)). 
+* Change dispatch of biomass and biogas generators in CBA by (a) setting the buses' marginal prices as the generators' marginal costs and (b) removing energy budget constraints ([#719](https://github.com/open-energy-transition/open-tyndp/pull/719)).
 
 **Bugfixes and Compatibility**