Some general rules apply:
- Sustainability impacts of the bio-energy production system are compared to those of the corresponding fossil reference system(s) as laid down in the RED (2009/28/EC) and report COM(2010).
- Wastes, agricultural crop residues, including straw, bagasse, husks, cobs and nut shells, and residues from processing, including crude glycerine (glycerine that is not refined), are considered to have zero impacts up to the process of collection of those materials. However, the use of those materials as non-artificial fertiliser for biomass production must be taken into account (see calculation sheet 'Global Warming').
- When during the entire bio-energy production process not only the desired final energy carriers are produced, but also other valuable products (co- or by-products), the impacts must be divided between the final fuel(s) and the co-products in proportion to their energy content. Or, in other words, allocation between final fuel(s) and co-products must be based on the lower heating value of the fuel(s)/products.
- Waste, including waste heat, and residues leave the system without allocation to it.
- Allocation takes place directly after a co-product is produced at a process step.
- For bio-energy installations producing electricity as well as useful heat, impacts are allocated based on the Carnot efficiency of the energy product.
- Impacts of the construction of buildings and production of machinery used for both bio-energy production and fossil reference energy production are not included in the calculations.
a) The energy balance
The energy balance of the process includes both the overall energy efficiency of the system, defined as the net energy ratio (NER) and the fossil energy reduction calculated through the non-renewable energy demand (NRED, here indicated as FER fossil energy requirement).
Both energy efficiency and reduction of fossil energy dependence are primary goals of the EU renewable energy strategy. It is therefore of crucial importance to take these issues into account while evaluating the sustainability of energy systems.
b) Calculation of Global Warming Potential (GWP)
The GWP is the sum of emissions of carbon dioxide (CO2), methane (CH4) and nitrogen oxides (N2O) into the atmosphere throughout the whole production chain. The calculation of the actual value of greenhouse gas (GHG) emissions is based on the EU guidelines on sustainability requirements for solid and gaseous biomass as prescribed in Annex V of the Renewable Energy Directive (2009/28/EC).
The GWP is expressed in CO2 equivalents and is deemed to be 23 for CH4 and 296 for N2O.
All terms are expressed per unit of fuel (CO2eq/MJ).
In case of byproducts, allocation factors are applied as explained in the previous under tool characteristics.
The emissions are calculated using standard values. Standard values are for instance the emissions of nitrous oxide or carbon dioxide per kilogramme of nitrogen fertiliser or per megajoule of natural gas. These are required to convert input numbers into GHG emissions. Companies normally can influence and measure input numbers, but cannot influence and/or measure standard conversion values. Standard conversion values have also been calculated using LCA analysis of both the processes that supply the inputs (like N-fertiliser and natural gas) and their emissions at combustion.
The standard values in the downloadable Excel file come mainly from two sources:
- the input data provided by the BioGrace Project: http://www.biograce.net/content/ghgcalculationtools/standardvalues;
- the standard values provided by the JEC consortium taken from the Well-to-Wheel study, WTT Appendix 1: http://ies.jrc.ec.europa.eu/WTW.
For more information on the detailed GHG emission calculation please see: PDF – GHG emission calculation.
c) Biodiversity and high carbon stocks
The B-SAT methodology to assess the impact of bioenergy production on biodiversity and high carbon stocks has been developed in such a way that it complies for as far as possible with the sustainability requirements on these topics within the Renewable Energy Directive.
In this Directive, Article 17 (3) regards land with high biodiversity and article 17 (4) and (5) contain requirements with respect to land with high carbon stock. Raw material for bioenergy production should not be taken from land that is identified by the Directive as land with high biodiversity value or from land that fell in January 2008 into one of the categories of land with high carbon stocks and no longer does. Although these requirements apply to biofuels for transport and bioliquids, the same requirements are recommended for the use of solid and gaseous biomass sources.
Land with high carbon stock includes wetlands, continuously forested areas and peatland.
Land with high biodiversity value includes primary forest and other primary wooded land, areas designated for nature protection purposes and highly biodiverse grassland.
Conformity is checked by means of the World Database on Protected Areas (WDPA: www.wdpa.org) and the Flemish Biological Valuation Map (BVM), which include areas designed for nature and endangered ecosystems and species protection (WDPA and BVM) as well as primary forest and highly biodiverse grasslands (only BVM).