ENEA-Italian National Agency for New Technologies, Energy and the Environment, Via Anguillarese 301, Rome, Italy.
JRC - Joint Research Center, European Commission, Italy.
J Environ Manage. 2024 Jul;364:121459. doi: 10.1016/j.jenvman.2024.121459. Epub 2024 Jun 12.
The current trend in the European biogas industry is to shift away from electricity production towards the production of biomethane for the need to replace natural gas. The upgrading of biogas to biomethane is normally performed by separating the biogas in a stream containing natural gas grid quality methane and a stream containing mostly CO. The CO stream is normally released into the atmosphere; however, part of the methane may still remain in it, and, if not oxidized, even a small fraction of methane released may jeopardise all the GHG emissions savings from producing the biomethane, being methane a powerful climate forcer. Scope of this work is to assess the opportunity cost of installing an Off Gas Combustion (OGC) device in biomethane upgrading plants. The currently available technologies for biogas upgrading to biomethane and the most common technology of OGC (the Regenerative Thermal Oxidisers, RTO) are described according to their performances and cost. Then the cost per tonne of COeq avoided associated to the adoption of RTO systems in relation to the upgrading performance is calculated to identify a potential threshold for an effective and efficient application of the RTO systems. It is found that, in case of upgrading technologies which can capture almost all biomethane in the upgrading off-gas (i.e. 99.9%), currently the adoption of an RTO to oxidise the methane left in the off-gas would add costs and need additional fuel to be operated, but would generate limited GHG emission savings, therefore the cost per tonne of COeq emissions avoided would result not competitive with other GHG emissions mitigation investments. While the installation of RTOs on upgrading systems with a methane slip of 0.3%, or higher, normally results cost competitive in reducing GHG emissions. The installation of an RTO on systems with a methane slip of 0.2% results in a cost per tonne of COeq emissions avoided of 50-100 euro, which is comparable to the current cost of CO emissions allowances in the EU ETS carbon market, representing therefore a reasonable choice for a threshold on methane slip regulation for biogas upgrading systems.
目前，欧洲沼气行业的发展趋势是从生产电力转向生产生物甲烷，以满足替代天然气的需求。沼气升级为生物甲烷通常是通过将含有天然气电网质量甲烷的气流与主要含有 CO 的气流分离来实现的。CO 气流通常被释放到大气中；然而，部分甲烷可能仍然存在，如果不被氧化，即使释放的甲烷很小一部分也可能危及生产生物甲烷所带来的所有温室气体排放节约，因为甲烷是一种强大的气候强迫因素。本工作的范围是评估在生物甲烷升级工厂中安装废气燃烧（OGC）装置的机会成本。根据其性能和成本，描述了目前用于沼气升级为生物甲烷的可用技术和最常见的 OGC 技术（蓄热式热力氧化器，RTO）。然后，计算与采用 RTO 系统相关的每吨 COeq 减排成本与升级性能的关系，以确定 RTO 系统有效和高效应用的潜在阈值。结果发现，在升级技术可以捕获升级废气中几乎所有生物甲烷的情况下（即 99.9%），目前采用 RTO 氧化废气中残留的甲烷将增加成本并需要额外的燃料来运行，但只会产生有限的温室气体排放节约，因此，每吨 COeq 减排成本将不具有竞争力，无法与其他温室气体减排投资相媲美。而在甲烷泄漏率为 0.3%或更高的升级系统中安装 RTO，通常可以在减少温室气体排放方面具有成本竞争力。在甲烷泄漏率为 0.2%的系统中安装 RTO，每吨 COeq 减排成本为 50-100 欧元，与欧盟 ETS 碳市场目前的 CO 排放配额成本相当，因此，对于生物甲烷升级系统的甲烷泄漏法规来说，这是一个合理的选择。
