Where the feasibility study is considering connection to a district heating system and this burns a mixture of fuels, only the proportion of output generated from second generation bio-fuels (or waste incineration that complies with BREEAM requirements) can be considered for this issue.
For instance, a system burning a 25/75 mix of compliant biofuel vs fossil fuel can only count 25% of its output towards a meaningful reduction in CO2 emissions (where relevant to the BREEAM scheme) against the baseline building.
As fuel mixes may vary over time, at least one year or more of historical information must be provided to balance out any seasonal variations. Where the system is new or proposed, robust evidence must be provided of the anticipated fuel mix.
The fuel mix must be calculated based on the energy content of the input fuels in kWh.
19/12/2017 Wording clarified