A cement-based geological disposal facility (GDF) is one potential option for the disposal of intermediate level radioactive wastes. The presence of both organic and metallic materials within a GDF provides the opportunity for both acetoclastic and hydrogenotrophic methanogenesis. However, for these processes to proceed, they need to adapt to the alkaline environment generated by the cementitious materials employed in backfilling and construction. Within the present study, a range of alkaline and neutral pH sediments were investigated to determine the upper pH limit and the preferred route of methane generation. In all cases, the acetoclastic route did not proceed above pH 9.0, and the hydrogenotrophic route dominated methane generation under alkaline conditions. In some alkaline sediments, acetate metabolism was coupled to hydrogenotrophic methanogenesis via syntrophic acetate oxidation, which was confirmed through inhibition studies employing fluoromethane. The absence of acetoclastic methanogenesis at alkaline pH values (>pH 9.0) is attributed to the dominance of the acetate anion over the uncharged, undissociated acid. Under these conditions, acetoclastic methanogens require an active transport system to access their substrate. The data indicate that hydrogenotrophic methanogenesis is the dominant methanogenic pathway under alkaline conditions (>pH 9.0).

水泥基地质处置设施（GDF）是处置中水平放射性废物的一种潜在选择。GDF中同时存在有机材料和金属材料，这为乙酰碎屑和氢营养甲烷生成提供了机会。但是，为了进行这些过程，它们需要适应回填和施工中所用胶结材料产生的碱性环境。在本研究中，对一系列碱性和中性pH沉淀物进行了研究，以确定pH上限和甲烷生成的优选途径。在所有情况下，在9.0以上的pH条件下，均未发生碎裂途径，而在碱性条件下，氢营养途径主导了甲烷的产生。在一些碱性沉积物中通过腐殖酸的乙酸氧化，这已通过使用氟甲烷的抑制研究得到证实。在碱性pH值（> pH 9.0）下没有破胶产甲烷作用是由于乙酸根阴离子比不带电荷的，未离解的酸占优势。在这些条件下，破骨细胞产甲烷菌需要主动转运系统才能接近其底物。数据表明，在碱性条件（> pH 9.0）下，氢营养型甲烷生成是主要的甲烷生成途径。