Environmental Flows¶

This guide covers working with biosphere exchanges - the emissions, resource consumption, and other environmental flows in your LCA models.

What are Environmental Flows?¶

Environmental flows (also called elementary flows or biosphere flows) represent exchanges between the industrial economy (technosphere) and the natural environment (biosphere):

Emissions: Substances released to air, water, or soil
Resources: Materials extracted from nature
Land use: Occupation and transformation of land

graph LR
    subgraph Technosphere
        A[Industrial<br/>Processes]
    end

    subgraph Biosphere
        B[Air]
        C[Water]
        D[Soil]
        E[Resources]
        F[Land]
    end

    A -->|Emissions| B
    A -->|Emissions| C
    A -->|Emissions| D
    E -->|Extraction| A
    F -->|Use| A

    style A fill:#e3f2fd
    style B fill:#ffebee
    style C fill:#e3f2fd
    style D fill:#efebe9
    style E fill:#e8f5e9
    style F fill:#fff3e0

Biosphere Structure¶

Environmental flows in ecoinvent are organized hierarchically:

Compartment
└── Sub-compartment
    └── Flow name

Main Compartments¶

Compartment	Description	Example Flows
Air	Emissions to atmosphere	CO₂, CH₄, NOₓ, particulates
Water	Emissions to water bodies	Phosphate, heavy metals, COD
Soil	Emissions to soil	Pesticides, heavy metals
Natural resource	Extractions from nature	Iron ore, crude oil, water
Land	Land occupation/transformation	Forest, agricultural land

Sub-compartments¶

Each compartment has specific sub-compartments:

AirWaterSoilNatural resource

low population density, long-term
lower stratosphere + upper troposphere
non-urban air or from high stacks
urban air close to ground
unspecified

ground-
ground-, long-term
lake
ocean
river
river, long-term
unspecified

agricultural
forestry
industrial
unspecified

biotic
fossil
in air
in ground
in water
land

Finding Biosphere Flows¶

Use search_biosphere to find the correct flow codes:

# Search for CO2 emissions
search_biosphere(
    q="carbon dioxide",
    database="ecoinvent-3.9.1-cutoff",
    compartment="air"
)

# Search for water emissions
search_biosphere(
    q="phosphate",
    database="ecoinvent-3.9.1-cutoff",
    compartment="water"
)

# Search with sub-compartment filter
search_biosphere(
    q="carbon dioxide",
    database="ecoinvent-3.9.1-cutoff",
    compartment="air",
    sub_compartment="urban air close to ground"
)

Common Flows¶

Category	Flow Name	Compartment	Typical Unit
GHG	Carbon dioxide, fossil	air	kg
GHG	Methane, fossil	air	kg
GHG	Dinitrogen monoxide	air	kg
Acidification	Sulfur dioxide	air	kg
Acidification	Nitrogen oxides	air	kg
Eutrophication	Phosphate	water	kg
Eutrophication	Nitrate	water	kg
Resources	Water, unspecified	natural resource/in water	m³
Resources	Crude oil	natural resource/in ground	kg

Adding Biosphere Exchanges¶

Direct Emissions¶

When your process directly emits substances:

# Step 1: Find the biosphere flow
result = search_biosphere(
    q="carbon dioxide fossil",
    database="ecoinvent-3.9.1-cutoff",
    compartment="air"
)
# Get the code from results, e.g., "349b29d1-3e58-4c66-98b9-9d1a076efd2e"

# Step 2: Create the exchange
create_database_exchange(
    activity_id="your-activity-uuid",
    amount=2.5,                    # 2.5 kg CO2 emitted
    exchange_type="biosphere",
    input_database="ecoinvent-3.9.1-cutoff",
    input_biosphere_code="349b29d1-3e58-4c66-98b9-9d1a076efd2e"
)

Resource Consumption¶

When your process directly consumes natural resources:

# Water consumption
create_database_exchange(
    activity_id="your-activity-uuid",
    amount=100.0,                  # 100 m³ of water
    exchange_type="biosphere",
    input_database="ecoinvent-3.9.1-cutoff",
    input_biosphere_code="water_flow_code"
)

Sign Convention for Biosphere¶

Positive Values

Use positive values for all biosphere exchanges:

✅ Emissions to environment: amount=2.5 (2.5 kg CO₂ released)
✅ Resource consumption: amount=100 (100 L water consumed)

The directionality is determined by the flow definition, not the sign:

Flow Type	Amount Sign	Meaning
Emission to air	Positive	Substance released to atmosphere
Emission to water	Positive	Substance released to water body
Resource from ground	Positive	Material extracted from earth
Resource from water	Positive	Water withdrawn from source

Choosing the Right Sub-compartment¶

The sub-compartment affects characterization factors in impact assessment:

Air Emissions¶

Sub-compartment	When to Use
`urban air close to ground`	Urban industrial processes, traffic
`non-urban air or from high stacks`	Power plants, large industrial facilities
`low population density, long-term`	Remote locations, long-term releases
`unspecified`	When location is unknown

Water Emissions¶

Sub-compartment	When to Use
`river`	Discharge to flowing water
`lake`	Discharge to standing freshwater
`ocean`	Marine discharge
`ground-`	Groundwater contamination
`unspecified`	When receiving water body is unknown

When in Doubt

Use unspecified if you're unsure about the exact sub-compartment. This is often the most common choice in generic LCA studies.

Impact Categories and Flows¶

Different impact assessment methods characterize different flows:

Climate Change (GWP)¶

Key flows:

Carbon dioxide, fossil
Methane, fossil
Dinitrogen monoxide (N₂O)
Hydrofluorocarbons (HFCs)
Perfluorocarbons (PFCs)
Sulfur hexafluoride (SF₆)

Acidification¶

Key flows:

Sulfur dioxide (SO₂)
Nitrogen oxides (NOₓ)
Ammonia (NH₃)
Hydrogen chloride (HCl)

Eutrophication¶

Key flows:

Phosphate (PO₄³⁻)
Nitrate (NO₃⁻)
Ammonia (NH₃)
Nitrogen oxides (NOₓ)
COD (Chemical Oxygen Demand)

Human Toxicity¶

Key flows:

Heavy metals (Pb, Cd, Hg, As)
Particulate matter (PM2.5, PM10)
Volatile organic compounds (VOCs)
Dioxins and furans

Working with Land Use¶

Land use flows are special biosphere exchanges:

Land Occupation¶

Time-integrated land use (area × time):

# Occupation of agricultural land for 1 year
search_biosphere(
    q="occupation, arable",
    database="ecoinvent-3.9.1-cutoff",
    compartment="natural resource"
)
# Unit: m²·year (or hectare·year)

Land Transformation¶

Change from one land type to another:

# Transformation from forest to agricultural land
search_biosphere(
    q="transformation, from forest",
    database="ecoinvent-3.9.1-cutoff",
    compartment="natural resource"
)
# Unit: m² (or hectare)

Best Practices¶

1. Match Specificity to Data Quality¶

# If you know the exact emission point:
sub_compartment="urban air close to ground"

# If you only have aggregate data:
sub_compartment=None  # Uses "unspecified"

2. Use Consistent Flow Names¶

Search for the exact flow name used in ecoinvent:

# ❌ May not find the right flow
search_biosphere(q="CO2")

# ✅ More specific, better results
search_biosphere(q="carbon dioxide, fossil")

3. Verify Units¶

Biosphere flows have specific units:

Flow Type	Common Units
Mass emissions	kg
Volume emissions	m³
Energy resources	MJ
Land use	m²·year, m²
Water	m³

4. Consider Upstream vs Direct¶

Many emissions come from upstream processes (electricity, materials) rather than direct releases:

graph TD
    A[Your Process] -->|Direct emissions| B[Biosphere]
    C[Electricity Production] -->|Upstream emissions| B
    D[Material Production] -->|Upstream emissions| B
    A -->|Input| C
    A -->|Input| D

    style A fill:#e3f2fd
    style B fill:#ffebee
    style C fill:#fff3e0
    style D fill:#fff3e0

Don't Double Count

If your material inputs are linked to ecoinvent activities, those activities already include their emissions. Only add direct biosphere exchanges for emissions that occur at your specific process.

Exploring Available Flows¶

Get All Compartments¶

get_biosphere_compartments(database="ecoinvent-3.9.1-cutoff")

Returns the complete hierarchy of compartments and sub-compartments.

Browse by Category¶

# All air emissions
search_biosphere(
    q="",  # Empty query
    database="ecoinvent-3.9.1-cutoff",
    compartment="air",
    limit=100
)

Troubleshooting¶

"Biosphere flow not found"¶

Check spelling matches ecoinvent exactly
Try searching with fewer words
Verify the compartment filter is correct

Zero impact for some categories¶

Your process may not emit relevant substances
Check if the correct biosphere flows are included
Verify the impact method includes characterization for your flows

Unexpectedly high/low impacts¶

Verify emission amounts and units
Check if the sub-compartment is appropriate
Compare with similar ecoinvent activities

Next Steps¶

Exchange Conventions - Sign conventions
Computational Structure - How calculations work
search_biosphere - Tool reference