Optimizing biogas production: an application to an Italian farming district

Biogas can be extracted from animal manure through anaerobic digestion (AD) and can afterwards be used to produce energy. Moreover, this process reduces completely methane emissions and stabilizes the manure before its agronomic use. AD plants can be built in a wide range of capacities: as capacity increases, economies of scale in capital equipment are realized, but transportation costs increase as manure and the digested substrates must be conveyed over longer distances. It is thus a key issue to assess the tradeoffs between biomass’ transportation and plants’ capacity. We propose a method to evaluate the AD plants’ convenience on a given territory by an economic, energy and emissive point of view. A mathematical model is formulated in order to optimize biomass use by finding the optimal AD plants’ number, capacity, location, and the corresponding biomass collection basin. The method is applied to the district of Cremona, one of the most important Italian farming areas. The optimal solution is achieved by widespread AD plants over the territory in order to exploit biomass locally. Biomass transportation is minimized for its high costs are not balanced by economies of scale. AD plants in Cremona yield positive returns in economic terms, as energy produced and GHG emissions avoided (7% reduction with respect to 2003). The robustness of this result has been confirmed by sensitivity analysis of the plant and transportation costs. The final result is crucial for local planning of biomass exploitation: local governments can encourage the development of conversion plants at municipal level without the need for centralized decisions.