Experimental conception and thermo-energetic analysis of a solar biogas production system

Solar biogas system production offers the possibility to simultaneously produce heat, electricity and to treat waste products as well as to reduce greenhouse gas emissions in the industrial sector. In this paper, we report on the development of an experimental solar biogas prototype to valorize the biomass generated by the Moroccan paper industry in order to reduce its carbon footprint. This paper presents an integrated solution to an environmental and energy problem of the companies that generate wet waste biomass. The current new prototype consists of a biogas production system using liquid biomass, a solar installation, and thermodynamic storage derived from a heat pump. Energy balances carried out show that the solar system can reach a thermal efficiency of 70%; the thermal losses of the system are around 53% for the biogas system and 22.6% for the storage and piping system. Further, the results found indicate the average heat demand of the digester reactor is 302 kWh per month, the solar system produced 284 kWh per month (94%) in worth case, which means the solar system is the main source energy and the system solar biogas is a self-energy system. Besides, it was found that the pilot solar biogas system produces about 1100 L of biogas, the analysis of biogas produced prove that it contains 74% of CH4 (814 L) and processes about 3000 L of industrial biomass daily, the biogas conversion efficiency of the whole system is 42%. The economic potential of the current solar biogas system in terms of electricity savings reached 2 MWh per month. The life cycle savings of the current solar system instead of purchasing electricity to meet the energy needs of the biogas process is approximately $4687. Annual emissions of (CO2), carbon monoxide (CO), and nitrogen oxides (NOx) are reduced by 69%, 71%, and 70% respectively. Upscaling the current prototype system to 700 m(3) (reactor volume) for the case study of cardboard company industry, shows that the yearly bio-methane (CH4) production is around 52,836 m(3) per year, which represent 64% of the total fuel consumption for the current case of cardboard recycling and packaging company.