Insights to improve covered lagoon biodigesters through by-products recovery in pig farms

Abstract

Pig farming activity has an important role in the Brazilian economy and generates effluents with a high polluting potential. The covered lagoon biodigester is a simple and suitable alternative for the treatment of swine manure. This work aimed to propose improvements to the pig effluent treatment system composed by covered lagoon biodigesters. Therefore, a survey of a typical plant configuration of pig effluent treatment was accomplished and alternatives were suggested in order to get a greater energy sustainability in farms through resource recovery. The proposed interventions were based on studies of scientific papers, technical equipment manuals, technical research and consultation with professionals of the field. The optimization of the systems operation considers some criteria, such as: (i) need for solids removal; (ii) organic loading; (iii) operation temperature; (iv) effluent recirculation; and (v) biogas energy recovery. Firstly, a typical scenario was identified without any improvements, in which the biogas is sent to flares without energy recovery. Subsequently, systems improvement insights were proposed, mainly regarding effluent heating through a solar heating system or by recovering the thermal energy from biogas and biogas recovering. The treatment optimization would increase the efficiency of organic matter removal and biogas production, as well as electric energy production and reduction in greenhouse gases emissions. The use of tools such as Life Cycle Analysis (LCA) can favor decision making and comparing proposed alternatives.