Method

Goal

Document every process step from site preparation to installation for seven biobased construction materials, with a traceable source and data-quality score for each number.

System boundary

Cradle to installed (A1 raw material supply, A2 transport to factory, A3 manufacturing, A4 transport to site, A5 installation). Use stage and end of life are out of scope.

A1: Growing, harvesting and raw materials: Raw material supply: site preparation, establishment, cultivation or forestry, harvest, field emissions, binder production
A2: Transport to the factory: Transport of raw materials to the factory
A3: Making the product: Manufacturing
A4: Transport to the building site: Transport to the construction site
A5: Building it in: Installation

What is left out

Manufacture of machinery, vehicles, factory buildings and forest roads (capital goods)
Staff commuting, offices and research
Use stage (B1-B7) and end of life (C1-C4, D); lime carbonation during use is shown as information only
Land-use change and soil carbon, listed as gaps where relevant because they are site-specific

No cut-off is applied to known flows. EN 15804 would allow omitting up to 1% per unit process and 5% in total; here every flow that could not be quantified is kept visible as a gap instead.

Allocation

Wood: mass allocation between products and sawmill co-products (EN 16485). Hemp: mass allocation between shiv, fibre and dust. Wheat straw and forest residues: burdens start at collection (choice flagged as the main sensitivity).

Biogenic carbon

Biogenic CO2 stored in the product is reported as a removal (EN 16449 for wood; 0.45 carbon fraction assumed for herbaceous materials). It is not netted against fossil GWP in the headline number.

EPD-calibrated residual

Where an EPD reports A1-A3 for a comparable product, the difference between the EPD and the characterised bottom-up flows can be shown as an 'EPD-calibrated residual'. It is off by default.

Provenance marks

Sourced: Sourced: value taken directly from the cited source
Derived: Derived: calculated from sourced values; formula shown
Proxy: Proxy: sourced value from a similar process or region
Assumption: Assumption: engineering assumption, edit per project
Gap: Gap: quantity or emission factor not found in open sources
Information: Information: step documented, no burden by definition

Data quality

Pedigree-style score 1 (best) to 5 (worst) combining reliability, completeness, and temporal, geographical and technological fit.

Calculation

For each flow: amount per declared unit = amount x conversion factor of its basis (for example hectares of crop per m3 of product). GWP = amount per declared unit x emission factor. The low and high ends combine the low and high amount with the low and high emission factor. Totals add characterised flows only.

Terms used on this site

Declared unit (DU): The amount of product all numbers refer to, here 1 m³ of installed material.
CO₂e and GWP100: Greenhouse gases converted to the warming effect of CO₂ over 100 years. One kg of N₂O counts as 273 kg CO₂e.
Fossil vs stored (biogenic) carbon: Fossil CO₂e comes from fuels, electricity, fertiliser and lime. Stored carbon was taken from the air by the plant and stays in the product while it exists.
Emission factor: kg CO₂e released per unit of an input, for example per litre of diesel.
EPD: Environmental Product Declaration: a verified LCA published by a manufacturer. Used here only as a check.
Flow: One input or emission of a process, such as diesel used by a baler.

Emission factors

Factor	Value	Unit	Range	Status	DQ	Source	Note
Diesel, non-road (GNR), combustion + upstream	3.16	kg CO2e/L	3.1–3.16	S	2	ADEME Base Empreinte (fuels)	ADEME Base Empreinte 'gazole non routier'. Used for all field, forest and site machinery.
Electricity, France average consumption mix 2024	0.058	kg CO2e/kWh	0.05–0.058	S	2	ADEME Base Empreinte (electricity 2024); ADEME Base Empreinte (fuels)	Declared geography is France. For plants outside France replace with the national mix.
Road freight, articulated truck 34-40 t	0.0875	kg CO2e/t.km	0.0875–0.0875	S	3	Truck 34-40 t default	Default value as reported by the cited page; verify against the current Base Empreinte release before publication.
Mineral N fertiliser (ammonium nitrate), production	3.6	kg CO2e/kg N	3.6–7.2	S	3	Yara AN footprint	3.6 = BAT plant. Upper bound 7.2 reflects the source statement that an average non-BAT European plant is about twice as high.
Field N2O (direct + indirect) per kg mineral N applied	5.894	kg CO2e/kg N	2.033–9.326	D	2	IPCC 2019 Refinement; IPCC AR6 GWP100	Derived: (EF1 0.010 + FracGASF 0.11 x EF4 0.010 + FracLEACH 0.24 x EF5 0.011) x 44/28 x 273. Range from EF1 uncertainty 0.001-0.018.
Hydrated lime Ca(OH)2, production (calcination + kiln fuel)	0.84	kg CO2e/kg	0.7454–0.9346	D	3	EC lime benchmark study; EMEP/EEA Guidebook lime	Derived: 56/74 kg CaO per kg Ca(OH)2 x (0.785 process + 0.20-0.45 fuel CO2 per kg CaO). Hydration, milling and packaging electricity excluded. Used as proxy for formulated lime binders (FL A 3.5) whose hydraulic fraction is not disclosed.
Conifer seedling produced, transported and planted (incl. protection)	0.5549	kg CO2e/seedling	0.5549–0.5549	D	3	Forests 2026, 17:316	Derived: 443.91 kg CO2e / 800 seedlings. Source functional unit also includes on-site chipping and plastic shelters, so the value is conservative. No range published; single value used.
Direct GWP value (aggregated proxy)	1	kg CO2e/kgCO2e	1–1	S	3	–	Used where a whole step is taken from an EPD module value.

Limitations

Proprietary databases (ecoinvent, Sphera) were not used. Flows without an open emission factor are listed as gaps and excluded from totals rather than estimated.
Only GWP is characterised. Other EN 15804 indicators need background data from a licensed database.
Several field-operation fuel values come from French machinery follow-ups for other crops and are marked as proxies.
Transport distances are assumptions and should be replaced by project data.