Modelling sustainability of a demand-based biomass to biogas conversion system: a bio-mimicry feedstock inventory-based approach

Biogas from anaerobic digestion of biomass is one of the potential renewable energy sources been considered for adoption in sub-Saharan Africa. Unfortunately, the issue of sustainability of feedstock supply in the biomass to biogas conversion system has been reported as one of the major factors militating against the adoption. Sometimes this challenge of not being able to meet feedstock demand is discovered during the production stage, as most designs reviewed did not incorporate a plan for sustainable supply of feedstock. Considering the enormous resources involved in the development of a bio-digester, it is, therefore, expedient to implement robust model(s) at the design stage, such that it can ascertain sustainability of continuous biomass supply necessary for meeting the biogas demand for all the specified periods. The concept of bio-mimicry with a focus on predator-prey interaction was adopted in developing an inventory-based model that enables the designers of the system to ascertain the critical start-up inventory of the prey(biomass) that will ensure sustained biogas production (predator existence) based on known demand level. The developed model was found useful in determining the minimum start-up biomass prior to production and in determining the level of sustainability for any given start-up inventory. It also provided the basis for decision-making in the commencement of biogas production from a given feedstock source.