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 effluentswith 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 thepig effluent treatment system composed by covered lagoon biodigesters. Therefore, a survey ofa typical plant configuration of pig effluent treatment was accomplished and alternatives weresuggested in order to get a greater energy sustainability in farms through resource recovery.The proposed interventions were based on studies of scientific papers, technical equipmentmanuals, technical research and consultation with professionals of the field. Th e 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 energyrecovery. Firstly, a typical scenario was identified without any improvements, in which the biogas is sent to flares without energy recovery. Subsequently, systems improvement insights wereproposed, mainly regarding effluent heating through a solar heating system or by recoveringthe thermal energy from biogas and biogas recovering. The treatment optimization wouldincrease the efficiency of organic matter removal and biogas production, as well as electricenergy production and reduction in greenhouse gases emissions. The use of tools such as LifeCycle Analysis (LCA) can favor decision making and comparing proposed alternatives.