Process Modeling Cookbook

"How do I model electricity consumption with regional grid mixes?" and "How do I account for transportation in complex supply chains?" are hands-on questions every practitioner faces. This cookbook provides practical recipes for common modeling challenges.

Recipe 1: Electricity with Regional Grid Mixes

The Challenge

Electricity impacts vary dramatically by region:

• Norway: ~20 g CO₂/kWh (hydro)
• France: ~60 g CO₂/kWh (nuclear)
• Germany: ~400 g CO₂/kWh (coal + renewables)
• Poland: ~700 g CO₂/kWh (coal)

Using the wrong grid mix can completely change your results.

Basic Recipe: Using Database Grid Mixes

Step 1: Identify the correct regional electricity process

In ecoinvent, electricity processes are named:

market for electricity, [voltage] | electricity, [voltage] | [location]

Voltage levels:

• High voltage: Transmission (large industry)
• Medium voltage: Distribution (manufacturing)
• Low voltage: End use (offices, homes)

Example selections:

Step 2: Apply appropriate voltage transformation losses

If your data is in primary energy, convert:

Delivered electricity = Primary energy × Grid efficiency (~35-40%)

Most databases already account for this—check your process documentation.

Advanced Recipe: Custom Grid Mix

When needed:

• Your country isn't in the database
• You have site-specific renewable energy
• You want to model future grid scenarios

Step 1: Get generation mix data Sources:

• IEA Electricity Information
• Ember Climate (free)
• National grid operator
• Company energy bills (for site-specific)

Step 2: Create custom process in openLCA/SimaPro

Custom process: "Electricity, medium voltage, Country X"

Inputs (per 1 kWh at medium voltage):
- Electricity, coal, at power plant: 0.45 kWh × 1.08 (losses) = 0.486 kWh
- Electricity, natural gas, at power plant: 0.30 kWh × 1.08 = 0.324 kWh
- Electricity, hydro, at power plant: 0.15 kWh × 1.08 = 0.162 kWh
- Electricity, solar, at power plant: 0.05 kWh × 1.08 = 0.054 kWh
- Electricity, wind, at power plant: 0.05 kWh × 1.08 = 0.054 kWh

Output:
- Electricity, medium voltage, Country X: 1 kWh

Note: The 1.08 multiplier accounts for ~8% transmission/distribution losses. Adjust based on actual regional data.

Recipe Variations

Scenario: On-site renewable energy

Site electricity = (% grid × grid process) + (% solar × solar process)

Scenario: Hourly matching (advanced) For time-sensitive analysis:

• Use hourly grid carbon intensity data
• Match consumption to generation profiles
• Consider marginal vs. average emissions

Recipe 2: Transportation in Complex Supply Chains

The Challenge

Real supply chains have:

• Multiple transport modes
• Varying distances
• Different vehicle types
• Return trips (often empty)

Basic Recipe: Single-Mode Transport

Formula:

Transport impact = Mass × Distance × Emission factor

Transport (tkm) = tonnes × kilometers

Database processes:

Example calculation:

Ship 5,000 kg of goods from China to Germany:

Step 1: Sea freight (Shanghai to Hamburg)
- Distance: ~20,000 km
- Transport: 5 t × 20,000 km = 100,000 tkm
- Process: transport, freight, sea, container ship

Step 2: Truck delivery (Hamburg to Munich)
- Distance: ~800 km
- Transport: 5 t × 800 km = 4,000 tkm
- Process: transport, freight, lorry >32t

Advanced Recipe: Full Supply Chain Logistics

Step 1: Map the logistics chain

Supplier → Port → Sea → Port → Warehouse → Factory
   ▲        ▲      ▲      ▲        ▲         ▲
  Truck   Truck   Ship  Truck   Truck     Internal
  (40km) (100km)       (50km)  (300km)

Step 2: Create transport sub-model

Step 3: Account for packaging and empty returns

Transport with packaging:
- Gross weight = Product (5t) + Packaging (0.5t) = 5.5t
- All tkm calculated on gross weight

Empty return (if applicable):
- Return trip at 20-50% load factor = partial impact
- Or use round-trip database processes

Recipe: Multi-Modal Decision Tool

Rule of thumb: Air freight ≈ 50× ocean freight per tkm.

Recipe 3: Cement and Concrete Manufacturing

The Challenge

Cement and concrete are critical for construction LCA but complex to model:

• Cement production has high process emissions (calcination)
• Concrete mixes vary widely
• Regional differences are significant

Basic Recipe: Using Database Cement

ecoinvent cement processes:

Simple concrete modeling:

1 m³ concrete ≈ 300-400 kg cement + 1,800 kg aggregates + 150 L water

Advanced Recipe: Custom Concrete Mix

Step 1: Get mix design data

Example ready-mix concrete (C30/37):
- Portland cement: 350 kg
- Fine aggregate (sand): 700 kg
- Coarse aggregate (gravel): 1,100 kg
- Water: 175 kg
- Admixtures: 3 kg

Step 2: Build custom process

Custom process: "Concrete, C30/37, Site-specific"

Inputs (per 1 m³):
- cement, Portland, local: 350 kg
- gravel, crushed: 1,100 kg
- sand: 700 kg
- tap water: 175 kg
- concrete admixture: 3 kg
- electricity, medium voltage: 5 kWh (mixing)

Output:
- Concrete, C30/37: 2,328 kg (≈1 m³)

Step 3: Add transport if not included

Transport of materials to batching plant:
- Cement from plant (50 km): 350 kg × 50 km = 17.5 tkm
- Aggregates local (20 km): 1,800 kg × 20 km = 36 tkm

Recipe: Low-Carbon Cement Alternatives

Supplementary cementitious materials (SCMs):

Modeling SCM blends:

Blended cement (CEM II/B-S):
- 65% Portland clinker
- 30% blast furnace slag
- 5% gypsum

Use weighted average of component impacts

Recipe 4: Manufacturing Processes

Generic Manufacturing Model

Template for any manufacturing process:

Manufacturing process template:

Inputs:
├── Materials
│   ├── Main material input: X kg
│   ├── Auxiliary materials: Y kg
│   └── Packaging materials: Z kg
├── Energy
│   ├── Electricity: A kWh
│   └── Thermal energy: B MJ
├── Water
│   └── Process water: C L
└── Transport
    └── Input materials: D tkm

Outputs:
├── Products
│   └── Main product: 1 unit
├── Co-products
│   └── Byproduct: E kg
├── Emissions (direct)
│   ├── CO₂: F kg
│   └── VOCs: G kg
└── Waste
    └── Production scrap: H kg

Recipe: Metal Fabrication

Example: Steel component manufacturing

Process: Steel bracket manufacturing (1 unit = 0.5 kg)

Inputs:
- Steel sheet, cold rolled: 0.6 kg (20% scrap rate)
- Electricity (cutting, forming): 0.3 kWh
- Lubricant: 0.005 kg
- Compressed air: 0.1 kWh electricity

Outputs:
- Steel bracket: 0.5 kg
- Steel scrap (to recycling): 0.1 kg
- Waste lubricant: 0.005 kg

Recipe: Plastic Injection Molding

Process: Injection molded part (1 unit = 0.1 kg)

Inputs:
- Polypropylene granules: 0.108 kg (8% process loss)
- Electricity (molding): 0.8 kWh
- Water (cooling): 5 L (closed loop, minimal loss)

Outputs:
- Molded part: 0.1 kg
- PP scrap (recycled internally): 0.008 kg

Recipe: Assembly Operations

For assembly (often overlooked):

Assembly process (1 unit)

Inputs:
- Components: From upstream processes
- Fasteners: X units (screws, rivets, etc.)
- Electricity: 0.1-1.0 kWh (tools, conveyors)
- Packaging: Y kg
- Compressed air: via electricity

Note: Assembly is often <5% of manufacturing impact.
Consider cut-off if not significant.

Recipe 5: End-of-Life Modeling

Waste Treatment Selection

Recipe: Multi-Path End-of-Life

Scenario: Product with mixed materials going to multiple fates

Product end-of-life breakdown:
- Total mass: 1 kg
  ├── Steel (0.5 kg): 80% recycled, 20% landfill
  ├── Plastic (0.3 kg): 50% recycled, 30% incinerated, 20% landfill
  └── Electronics (0.2 kg): 60% WEEE recycling, 40% landfill

Waste treatment processes needed:
- treatment of scrap steel: 0.5 × 0.8 = 0.4 kg
- treatment of steel to landfill: 0.5 × 0.2 = 0.1 kg
- treatment of waste plastic, recycling: 0.3 × 0.5 = 0.15 kg
- treatment of waste plastic, incineration: 0.3 × 0.3 = 0.09 kg
- treatment of waste plastic, landfill: 0.3 × 0.2 = 0.06 kg
- treatment of WEEE: 0.2 × 0.6 = 0.12 kg
- treatment of electronics to landfill: 0.2 × 0.4 = 0.08 kg

Common Modeling Pitfalls

Pitfall 1: Wrong voltage level for electricity

Wrong: Using high voltage for office building Right: Low voltage for offices, medium voltage for factories

Pitfall 2: Forgetting transport

Wrong: Materials appear at factory gate by magic Right: Include transport for all purchased materials

Pitfall 3: Double-counting recycling

Wrong: Recycled input burden-free AND recycling credit at end-of-life Right: Choose one approach consistently

Pitfall 4: Ignoring packaging

Wrong: Only modeling the product itself Right: Include primary, secondary, and tertiary packaging

Pitfall 5: Using annual instead of per-unit data

Wrong: "Factory uses 1 GWh/year electricity" Right: "Product uses 0.5 kWh/unit" (calculate from production volume)

Key Takeaways

1. Electricity grid mix significantly affects results—use correct regional data
2. Transport modeling requires mode, distance, and vehicle type
3. Cement/concrete has high process emissions—use specific mix designs when available
4. Manufacturing processes follow a template: materials + energy + water → product + waste
5. End-of-life requires fate percentages for each material stream
6. Document everything—assumptions, sources, and calculations

Modeling Checklist

For each process in your model:

☐ Correct geographic process selected ☐ Appropriate voltage level for electricity ☐ Transport included for material inputs ☐ Direct emissions estimated or measured ☐ Waste/byproduct treatment included ☐ Data scaled to functional unit ☐ Mass balance verified (inputs ≈ outputs)

---

Next Steps

With modeling recipes in hand, the next lesson covers Result Validation & Troubleshooting—how to check your results make sense and diagnose common problems.