Techno-economic feasibility assessment of renewable electrical and thermal energy supply options for biomethane production plants

Bioenergy, solar energy and geothermal energy are among the most important types of renewable energy sources, which contribute to a more efficient energy use, climate change mitigation, and environmental protection. Upgrading biogas to biomethane production has become one of the most interesting targets in recent years, as a proper alternative source for fossil fuels. Despite this method is highly efficient process, it requires a high thermal energy demand for anaerobic digestion in addition to more required electricity required for upgrading biogas into the biomethane. This study investigates two methods of utilizing biogas: converting the total biogas into the biomethane and converting a portion of the biogas into the biomethane and the remainder is used in a combined heat and power (CHP) generation. The energy demand of fully biomethane production plants is supplied by the national grid, a heat pump, photovoltaic panels system, and combination of a heat pump and photovoltaic panels (scenarios one to four). The energy demand for the combination of and biomethane production plants is supplied by a combination of CHP generation and a heat pump or a combination of CHP generation and a biogas boiler (scenarios five and six). Organic fraction of municipal solid waste (OFMSW), livestock, wastewater sludge (WWS) and mixture of different feedstocks are considered as different feedstocks for each of the mentioned scenarios. The feedstocks need various electrical and thermal energy demand considering different biomethane productivity per unit of feedstocks mass (BMP). Economic analysis is also conducted to determine the most efficient scenarios and feedstocks for biomethane production based on different electricity prices: typical electricity prices of Italy and France. The results show that employing a heat pump and photovoltaic panels system are a viable and efficient technology for the typical electricity price in Italy. However, employing photovoltaic panels system is not recommended for typical electricity cost in France, due to the high cost of photovoltaic panels systems instalments and maintenances compared to the electricity price of France.