Faragò Maria, Damgaard Anders, Rebsdorf Morten, Nielsen Per Henrik, Rygaard Martin
Department of Environmental and Resource Engineering, Water Technology and Processes, Technical University of Denmark, Bygningstorvet, Building 115, 2800, Lyngby, Denmark.
Department of Environmental and Resource Engineering, Circularity and Environmental Impact, Technical University of Denmark, Bygningstorvet, Building 115, 2800, Lyngby, Denmark.
J Environ Manage. 2022 Oct 15;320:115715. doi: 10.1016/j.jenvman.2022.115715. Epub 2022 Aug 8.
Wastewater treatment is an important source of direct and indirect greenhouse gas (GHG) emissions, which some wastewater operators report and account for CO-eq impacts through carbon footprint evaluations. We investigated the challenges with GHG emissions' accounting of three state-of-the-art energy-efficient wastewater resource recovery facilities (WRRFs) and reviewed their CO accounting reports. Our study aimed to highlight the major contributors and factors to estimate emissions, including direct NO and CH emissions and propose recommendations for public reporting of CO accounting of WRRFs. We categorised emissions as direct (scope 1), background (scope 2), downstream and avoided emissions (scope 3A and 3B) and evaluated how a change in emission factor may affect how close the WRRFs are to reaching CO neutrality. The results show that electricity consumption and direct emissions constitute between 20 and 70% of actual CO-eq emissions and therefore need careful consideration. All three plants have increasingly offset scope 2 emissions over 2014-2019, resulting in a total reduction of approximately 3211 tons CO-eq, corresponding to 72% of their needed cuts by 2030 set by the Danish government. No standard factors are used across the plants to estimate emissions. We propose some general recommendations that wastewater operators can apply to correctly report and account for CO-eq emissions. We also recommend that operators move their long-term focus from CO neutrality to CO-eq reduction and make an effort to measure and quantify scope 1 direct emissions properly. A tax on NO emissions should be introduced in future policies.
废水处理是直接和间接温室气体排放的一个重要来源，一些废水处理运营商通过碳足迹评估报告并核算其二氧化碳当量影响。我们调查了三个先进的节能废水资源回收设施（WRRFs）在温室气体排放核算方面面临的挑战，并审查了它们的二氧化碳核算报告。我们的研究旨在突出估算排放的主要贡献者和因素，包括直接的一氧化二氮和甲烷排放，并就WRRFs二氧化碳核算的公开报告提出建议。我们将排放分为直接排放（第1类）、背景排放（第2类）、下游排放和避免排放（第3A类和第3B类），并评估排放因子的变化可能如何影响WRRFs接近实现碳中和的程度。结果表明，电力消耗和直接排放占实际二氧化碳当量排放的20%至70%，因此需要仔细考虑。在2014 - 2019年期间，所有三个工厂对第2类排放的抵消量都在增加，总共减少了约3211吨二氧化碳当量，相当于丹麦政府设定的到2030年所需减排量的72%。各工厂在估算排放时未使用统一的标准因子。我们提出了一些一般性建议，废水处理运营商可应用这些建议正确报告和核算二氧化碳当量排放。我们还建议运营商将长期重点从碳中和转向减少二氧化碳当量排放，并努力正确测量和量化第1类直接排放。未来政策应引入一氧化二氮排放税。
