DataSheet1_v1_Life Cycle Assessment of Power-to-Syngas: Comparing High Temperature Co-Electrolysis and Steam Methane Reforming.docx

To achieve the European Union’s ambitious climate targets, not only the energy system must be transformed, but also other sectors such as industry or transport. Power-to-X (PtX) technologies enable the production of synthetic chemicals and energy carriers using renewable electricity, thus contributing to defossilization of economy. Additionally, they provide storage capacity for renewable energy. Detailed life cycle assessments (LCA) of PtX is required, to prove the environmental advantages to fossil-based benchmark technologies. An emerging PtX technology for syngas production is the high temperature co-electrolysis (HT-co-electrolysis), which produces syngas. Aim of this LCA is the evaluation of syngas production by HT-co-electrolysis at its early stage of development to derive incentives for further research. For comparison, a small-scale steam methane reforming process (SMR) serves as today’s fossil-based benchmark. The required CO2 is obtained via direct air capture. The by-far most important input for the HT-co-electrolysis is electricity. Hence, several future electricity mixes are considered, representing two different climate protection targets (CPT80, CPT95) for the energy system in 2050. For each CPT, an additional distinction is made regarding full load hours, which depend on the availability of renewable energy. The results show lower global warming potential (GWP) and fossil fuel depletion for HT-co-electrolysis compared to SMR if mostly renewable power is used. Exclusively renewable operated HT-co-electrolysis even achieve negative net GWPs in cradle-to-gate LCA without considering syngas use. If HT-co-electrolysis shall operate continuously (8,760 h) additional fossil electricity production is needed. For CPT80, the share of fossil electricity is too high to achieve negative net GWP in contrast to CPT95. Other environmental impacts such as human toxicity, acidification, particulate matter or metal depletion are worse in comparison to SMR. The share of direct air capture on the total environmental impacts is quite noticeable. Main reasons are high electricity and heat demands. Although plant construction contributes to a minor extent to most impact categories, a considerable decrease of cell lifetime due to higher degradation caused by flexible operation, would change that. Nevertheless, flexibility is one of the most important factors to apply PtX for defossilization successfully and reinforce detailed research to understand its impacts.

为达成欧盟雄心勃勃的气候目标，不仅能源系统亟需转型，工业、交通等其他领域也需推进变革。电转X（Power-to-X, PtX）技术可依托可再生电力合成化学品与能源载体，助力经济脱碳，同时还能为可再生能源提供存储容量。为证明其相较于化石基基准技术的环境优势，需对PtX技术开展详细的生命周期评估（LCA）。
当前新兴的合成气生产PtX技术为高温共电解（HT-co-electrolysis），可直接产出合成气。本生命周期评估旨在对处于研发早期阶段的高温共电解合成气生产技术进行评估，以明确可推动其进一步研究的激励方向。作为对照，本次研究以当前主流的化石基基准技术——小型蒸汽甲烷重整工艺（SMR）作为参照。研究所需的二氧化碳通过直接空气捕获获取。
迄今为止，高温共电解最为核心的输入为电力，因此本次研究考虑了多种未来电力结构，分别对应2050年欧盟能源系统的两类不同气候保护目标（CPT80、CPT95）。针对每一类气候保护目标，还会根据可再生能源的可获得性，进一步按满负荷运行小时数进行区分。
结果显示，若主要使用可再生电力，高温共电解工艺的全球变暖潜势（GWP）与化石燃料消耗均低于蒸汽甲烷重整工艺。仅使用可再生电力运行的高温共电解工艺，在不考虑合成气后续使用的“从摇篮到大门”生命周期评估中，甚至可实现净全球变暖潜势为负值。若高温共电解工艺需持续满负荷运行（8760小时），则需额外补充化石电力生产。相较于CPT95目标，CPT80目标下的化石电力占比过高，无法实现净全球变暖潜势为负值。
在其他环境影响维度，如人体毒性、酸化、颗粒物排放与金属消耗方面，高温共电解工艺的表现均劣于蒸汽甲烷重整工艺。直接空气捕获环节对总环境影响的占比较为显著，主要原因是其对电力与热力的需求较高。尽管工厂建设环节对多数影响类别的贡献较小，但若因柔性运行导致的更高退化速率大幅缩短电解池寿命，则会改变这一情况。不过，柔性运行是成功利用PtX技术实现经济脱碳的关键因素之一，因此亟需开展更深入的研究以明确其环境影响。