energyLS · energyLS · Aug 31, 2026 · Aug 31, 2026 · Aug 31, 2026 · Aug 31, 2026
diff --git a/README.md b/README.md
@@ -1,5 +1,8 @@
 # SHIFT – Steel & Hydrogen Integrated Freight Trade
 
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.21875103.svg)](https://doi.org/10.5281/zenodo.21875103)
+
 **SHIFT** is a spatially resolved techno-economic optimization of global iron
 and steel supply chains under decarbonization. It explores how
 hydrogen-based direct reduced iron (DRI) production and hot-briquetted iron
@@ -10,6 +13,8 @@ orchestrated with [Snakemake](https://snakemake.readthedocs.io/).
 
 ## Quick start – installation & execution
 
+SHIFT requires Python 3.10+ and uses [pixi](https://pixi.sh/latest/installation/) to manage the environment. Install pixi before you continue.
+
 ```sh
 git clone https://github.com/energyLS/shift.git
 cd shift
@@ -20,12 +25,16 @@ pixi run snakemake model_trade_all
 Approximate runtimes:
 
 - Installation (`pixi install`): ~5 minutes
-- Full model (`model_trade_all`): ~5 hours
+- Demo model (this branch): ~1 hour
+
+By default, the model solves with [HiGHS](https://highs.dev/), a license-free
+solver. If you have a [Gurobi](https://www.gurobi.com/) license, set
+`solver.name: gurobi` in `config/config.yaml` for faster solves.
 
-> [!TIP]
-> For a quick, low-resolution run, check out the
-> [`demo` branch](https://github.com/energyLS/shift/tree/demo), which uses
-> fewer regions and quantities and completes in ~1 hour.
+> [!NOTE]
+> This is the `demo` branch: it uses fewer regions and quantities so it
+> runs much faster. For the full-resolution model (~5 hours), see the
+> [`main` branch](https://github.com/energyLS/shift/tree/main).
 
 ## Key results
 

diff --git a/config/config.yaml b/config/config.yaml
@@ -135,7 +135,7 @@ scenario:
 # Absolute steel demand levels (Mt/year) for supply curve sweep
 # For each level, PyPSA minimizes cost with fixed renewable capacity
 # Values represent different production scales
-steel_demand_levels: [0.1, 0.5, 1, 5, 10, 25, 50, 75, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000] # Mt/year
+steel_demand_levels: [1, 10, 100, 1000] #[0.1, 0.5, 1, 5, 10, 25, 50, 75, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000] # Mt/year
 
 electricity_steel_ratio: 5.25 #TWh/Mt or MWh/t, see notebooks 'analysis-steel.ipynb'
 embodied_energy_steel: 2.1 #TWh/Mt or MWh/t, see iron oxide reduction
@@ -144,19 +144,19 @@ embodied_energy_steel: 2.1 #TWh/Mt or MWh/t, see iron oxide reduction
 # Region definitions (ISO3 codes matching renewable clusters metadata)
 regions:
   "Europe": ["ALB","AUT","BLR","BEL","BIH","BGR","HRV","CYP","CZE","DNK","EST","FIN","DEU","GRC","HUN","ITA","XKX","LVA","LTU","LUX","MKD","MDA","MNE","NLD","NOR","POL","ROU","SRB","SVK","SVN","SWE","CHE","TUR","UKR"]
-  "Far_West_Europe": ["FRA","GRL","ISL","IRL","PRT","ESP","GBR"]
-  "Middle_East": ["BHR","IRN","IRQ","ISR","JOR","KWT","LBN","OMN","PSE","QAT","SAU","SYR","ARE","YEM"]
-  "North_West_Africa": ["BEN","BFA","CIV","GMB","GHA","GIN","GNB","LBR","NGA","SEN","SLE","TGO","DZA","TCD","EGY","ERI","LBY","MLI","MRT","MAR","NER","SDN","TUN","ESH"]
-  "Subsaharan_Africa": ["AGO","BWA","BDI","CMR","CAF","COD","ETH","KEN","GAB","MDG","MWI","MOZ","NAM","COG","RWA","SOM","ZAF","SSD","TZA","UGA","ZMB","ZWE"]
+  # "Far_West_Europe": ["FRA","GRL","ISL","IRL","PRT","ESP","GBR"]
+  # "Middle_East": ["BHR","IRN","IRQ","ISR","JOR","KWT","LBN","OMN","PSE","QAT","SAU","SYR","ARE","YEM"]
+  # "North_West_Africa": ["BEN","BFA","CIV","GMB","GHA","GIN","GNB","LBR","NGA","SEN","SLE","TGO","DZA","TCD","EGY","ERI","LBY","MLI","MRT","MAR","NER","SDN","TUN","ESH"]
+  # "Subsaharan_Africa": ["AGO","BWA","BDI","CMR","CAF","COD","ETH","KEN","GAB","MDG","MWI","MOZ","NAM","COG","RWA","SOM","ZAF","SSD","TZA","UGA","ZMB","ZWE"]
   "North_America": ["CAN","USA"]
-  "Eurasia": ["ARM","AZE","GEO","KAZ","KGZ","TJK","TKM","UZB","RUS"]
-  "South_America": ["BOL","BRA","COL","ECU","GUF","GUY","PRY","PER","SUR","VEN"]
-  "South_South_America": ["ARG","CHL","URY"]
-  "Central_America": ["CRI","SLV","GTM","HND","MEX","NIC","PAN","CUB","DOM","JAM","HTI"]
-  "West_Asia": ["AFG","BGD","BTN","IND","NPL","PAK","LKA"]
-  "East_Asia": ["CHN","HKG","MNG","TWN"]
-  "Pacific_Asia": ["BRN","KHM","IDN","LAO","MYS","MMR","PNG","PHL","SGP","THA","VNM"]
-  "East_East_Asia": ["JPN","KOR","PRK"]
+  # "Eurasia": ["ARM","AZE","GEO","KAZ","KGZ","TJK","TKM","UZB","RUS"]
+  # "South_America": ["BOL","BRA","COL","ECU","GUF","GUY","PRY","PER","SUR","VEN"]
+  # "South_South_America": ["ARG","CHL","URY"]
+  # "Central_America": ["CRI","SLV","GTM","HND","MEX","NIC","PAN","CUB","DOM","JAM","HTI"]
+  # "West_Asia": ["AFG","BGD","BTN","IND","NPL","PAK","LKA"]
+  # "East_Asia": ["CHN","HKG","MNG","TWN"]
+  # "Pacific_Asia": ["BRN","KHM","IDN","LAO","MYS","MMR","PNG","PHL","SGP","THA","VNM"]
+  # "East_East_Asia": ["JPN","KOR","PRK"]
   "Oceania": ["AUS","NZL"]
 
 region_nice_names:
@@ -254,8 +254,9 @@ plot:
       bus_size: 2.0e-7
       link_width: 3.0e-8
 solver:
-  name: gurobi
-  options: gurobi-default
+  name: highs  # license-free by default; set to "gurobi" (with a valid license) for faster solves
+  options: highs-default  # used for the trade LP, where crossover-derived duals (nodal prices) matter
+  options_lcox: highs-lcox  # used for regional LCOX/supply-curve solves, which only consume the primal solution
   compute_iis: False  # Set to false to skip expensive IIS computation for infeasible models
 solver_options:
     highs-default:
@@ -270,6 +271,21 @@ solver_options:
       ipm_optimality_tolerance: 1e-6
       parallel: "on"
       random_seed: 123
+    highs-lcox:
+      # No crossover: calculate_lcox.py only reads network.objective and the
+      # primal capacity mix, never duals, so a basic (vertex) solution is not
+      # required and skipping crossover saves the simplex clean-up pass.
+      # solver left as "choose" so HiGHS can pick simplex over IPM where cheaper.
+      threads: 4
+      solver: "choose"
+      run_crossover: "off"
+      small_matrix_value: 1e-6
+      large_matrix_value: 1e15
+      primal_feasibility_tolerance: 1e-6
+      dual_feasibility_tolerance: 1e-6
+      ipm_optimality_tolerance: 1e-5
+      parallel: "on"
+      random_seed: 123
     gurobi-default:
       threads: 4
       method: 2 # barrier
@@ -360,4 +376,4 @@ colors:
   # Friendshoring colors
   bloc_1: "#17679E"         # Europe (Western bloc: Europe + Far West Europe + North America)
   bloc_2: "#8352D8"         # Middle_East (Global South bloc)
-  bloc_3: "#BF9A39"         # East_East_Asia (East Asia + Oceania bloc)
+  bloc_3: "#BF9A39"         # East_East_Asia (East Asia + Oceania bloc)
diff --git a/rules/retrieve.smk b/rules/retrieve.smk
@@ -3,11 +3,10 @@ storage:
     keep_local=True,
     retries=3,
 
+
 rule retrieve_data:
     input:
-        data_url=storage(
-            f"https://zenodo.org/records/21875103/files/shift_data.zip"
-        ),
+        data_url=storage(f"https://zenodo.org/records/21875103/files/shift_data.zip"),
     output:
         bus_locations="data/bus_locations.csv",
         ip_market_fabrication="data/demand/ip_market__fabrication.csv",
@@ -17,6 +16,7 @@ rule retrieve_data:
         unido_raw="data/labour/unido-raw/data.csv",
         iron_ore_production="data/owid-iron-ore/iron-ore-crude-ore-production.csv",
         political_stability="data/political-stability/globaleconomy.csv",
+        trade_opt="data/trade_opt.csv",
         renewable_profiles_geojson="data/renewable_profiles_global_merged.geojson",
         renewable_profiles_nc="data/renewable_profiles_global_merged.nc",
     log:
@@ -27,4 +27,4 @@ rule retrieve_data:
     params:
         folder=".",
     run:
-        unpack_archive(input.data_url, params.folder)
+        unpack_archive(input.data_url, params.folder)
diff --git a/workflow/scripts/calculate_lcox.py b/workflow/scripts/calculate_lcox.py
@@ -365,7 +365,8 @@ def solve_network(network, config):
     solver_cfg = config.get("solver", {})
     solver_name = os.getenv("SHIFT_SOLVER", solver_cfg.get("name", "glpk"))
     solver_options_key = os.getenv(
-        "SHIFT_SOLVER_OPTIONS", solver_cfg.get("options", "default")
+        "SHIFT_SOLVER_OPTIONS",
+        solver_cfg.get("options_lcox", solver_cfg.get("options", "default")),
     )
     solver_options = config.get("solver_options", {}).get(solver_options_key, {})