*3.2. Environmental Results*

A CO2 balance that fully assesses the CO2 inputs and outputs of the scenarios under investigation is presented in Table 6. The methodology undertaken was a "cradle-to-grave" approach to provide an accurate representation of the net CO2- savings for each of the SSAD scenarios per year.


**Table 6.** Annual CO2 balance for scenarios under study.

a Diesel consumption per car is reported to be 1259 litres yr<sup>−</sup>1, as reported in the literature [80].

All scenarios investigated exhibited a net CO2 reduction, ranging between 2059–173,237 kg CO2-eq yr<sup>−</sup>1. Significant net CO2 savings were shown for each of the scenarios under investigation, even in the smallest farm size investigated (Scenario 1), with savings of 41,180 kg CO2-eq. over the lifespan of the plant (equivalent to taking 87 cars o ff the road). This shows that SSAD can have a meaningful contribution, even at relatively small sizes. The activity which resulted in the largest production of CO2 emissions was the "Biogas Production Process", where the release of CO2 in the combustion of biogas contributed approximately 90% to 95% of the total CO2 emissions released per annum.
