Life cycle greenhouse gas emissions from geothermal electricity production

Abstract

A life cycle analysis (LCA) is presented for greenhouse gas (GHG) emissions and fossil energy use associated with geothermal electricity production with a special focus on operational GHG emissions from hydrothermal flash and dry steam plants. The analysis includes results for both the plant and fuel cycle components of the total life cycle. The impact of recent changes to California's GHG reporting protocol for GHG emissions are discussed by comparing emission rate metrics derived from post and pre revision data sets. These metrics are running capacity weighted average GHG emission rates (g/kWh) and emission rate cumulative distribution functions. To complete our life cycle analysis, plant cycle results were extracted from our previous work and added to fuel cycle results. The resulting life cycle fossil energy and greenhouse gas emissions values are compared among a range of fossil, nuclear, and renewable power technologies, including geothermal. V C 2013 AIP Publishing LLC. [http://dx.NOMENCLATURE Bio-UB electricity from a biomass fired utility boiler Bio-IGCC electricity from a biomass fired IGCC plant CDF emission rate cumulative distribution function CSP concentrated solar power E out power plant output energy in kWh over its lifetime EGS enhanced geothermal systems E pc plant cycle fossil energy consumption E fc fuel cycle fossil energy consumption e pc plant cycle energy ratio: E pc /E out e fc fuel cycle energy ratio: E fc /E out fc denotes fuel cycle fp denotes fuel production fu denotes fuel use g g r a m s GHG pc plant cycle greenhouse gas emissions GHG fc fuel cycle greenhouse gas emissions ghg pc plant cycle GHG emissions ratio: GHG pc /E out ghg fc fuel cycle GHG emissions ratio: GHG fc /E out GREET greenhouse gas regulated emissions and energy use in transportation model HT-F hydrothermal flash HT-B hydrothermal binary IGCC integrated gasification combined cycle plant LCA life cycle analysis LCI life cycle inventory m meter NGCC natural gas combined cycle

High-Temperature Geothermal Utilization in the Context of European Energy Policy—Implications and Limitations

“…The utilization of geothermal resources generally results in low emissions of GHG compared to conventional energy resources (e.g., [17,36,37]). The highest emissions from geothermal exploitation stem from utilizing high-temperature resources [8].…”

Deep geothermal energy extraction, a review on environmental hotspots with focus on geo-technical site conditions

“…The direct emissions of GHGs (mainly CO2 and CH4) lead to the high GW impact in these plants. Note that for one plant the direct emissions were not reported, although the authors stated that they are the main cause of the GW impact [43]. When the outlier point are excluded the GW impact ranges from 3.9 to 245 g CO2-eq/kWh and the average value is 86 g CO2-eq/kWh.…”

“…One study on dry steam plants adopted a cradle to grave approach, and also evaluated the plant's sustainability in terms of resources use by emergy analysis [16]. Two other studies focused on the operational impact, using annual monitored direct emissions data, from three plants in Italy [38] and four plants in the USA [43]. Only two studies [16,38] reported geo-technical data of the plant (Table 3).…”

“…Meanwhile, a study that did not report emissions of Ni or Cr found a low HT impact [37] (Tables 7-8). Another four studies attributed the GW impact to GHG direct emissions [17,33,42,43]; one of these also attributed the AC, HT and FWEC impacts to NCG direct emissions [42]. In addition, the scenario analysis performed in [37] shows that reducing the direct emissions, through abatements systems, or considering a part of them to be natural leads to much lower GW and AC impacts.…”

Geothermal Energy as an Alternative to Reduce Atmospheric Emissions and Provide Green Energy

“…The use of geothermal resources has shown technical and economic viability to produce energy with a sustainable conscience, and in this context, it has been considered that the energy extracted from this system can be recuperated in a time scale similar to the process of its extraction [26]. In studies on the life-cycle analysis, it has been shown that the production of electricity affects the environment very mildly since its discharge is mainly wet steam and low gas emissions [27]. This makes it environmentally conscious.…”