*3.1. Technical Results*

The technical parameters of the SSAD plants under study are presented in Table 5. These parameters provide an overview of the plant's operation in terms of feedstock used, plant specifications, resulting methane yield and application of energy. The cow manure available increased linearly, as it was directly proportional to the number of livestock on the farm. Interestingly, the farmland available for biogas production increased by just 35.4% between the smallest and largest farm sizes, showing that a larger proportion of farmland is potentially available for biogas production in farms with smaller herd sizes. Consequently, the grass feedstock represented a much larger percentage of total methane production in Scenario 1 (51%) in comparison to Scenario 5 (23%).


**Table 5.** Technical characteristics of scenarios under study.

a Methane yield utilised by the CHP unit annually; b Electricity consumption of an average residential house was assumed to be 4200 kWh yr<sup>−</sup><sup>1</sup> [79]; c Heat consumption of an average residential house was assumed to be 11,000 kWh yr<sup>−</sup><sup>1</sup> [79].

All scenarios examined exhibited a net energy generation, which was used to supply external applications, as shown in Figure 4. The farm's energy demand represented a relatively small portion of the total energy generated, ranging from 3.08% to 4.66%. The majority of the energy generated was exported off-site, representing between 73.04% and 79.13% of the total energy generated, demonstrating the need for external applications at the plants' planning stage.

**Figure 4.** Final electrical and thermal energy usage via the combined heat and power (CHP) unit.
