Integrated environmental accounting of a geothermal grid

The worldwide energy consumption shows a significant increasing demand and is still projected to grow in the next years. This is causing increased pollution and environmental degradation. The energy sector is one of the major contributors to the emissions of greenhouse gases and pollutants. A fair access for everyone to energy sources capable of meeting the global needs without further degrading the ecosystems is of paramount importance. In this work, a sustainable medium enthalpy geothermal system to produce electric and thermal energy is assessed. The case study is located in Campania region, Southern Italy, in an area famous for its volcanic activity. The system is composed by an Organic Rankine Cycle for electricity production and a grid for district heating and cooling. The environmental performances are assessed using the Emergy Accounting (EMA) systemic approach. The calculation of the EMA conversion factors, the so-called Unit Emergy Values (UEVs), could benefit from the use of appropriate inventories. The databases used within the Life Cycle Assessment (LCA) method provide a huge amount of reliable, peer reviewed inventories. This work proposes the use of LCA inventories to calculate UEVs, comparing them to literature ones. The performance of the investigated system is calculated and compared to current and improved strategies for heating and cooling and electricity production. The calculated UEVs seem to be reliable when compared to literature values, strengthening the link between LCA and EMA methods. The obtained results confirm the environmental feasibility of the analyzed system and its beneficial environmental performance, when compared to fossil based and other renewable energy production systems. The electricity, heating and cooling produced by the investigated system has UEV values of respectively 1.0E+04, 7.6E+03 and 1.1E+04 sej/J, validating its fitness within a perspective of improved sustainability.