Carbon dioxide emission reduction from anaerobic digesters by calcium carbonate precipitation with waste cementitious materials.

加拿大人口稠密的城市在市政污水处理厂(WWTP)处理污水。一些市政当局使用厌氧消化(AD)来稳定下水道污泥。AD尾气的体积约为65%的甲烷和35%的二氧化碳。甲烷(“生物甲烷”或“沼气”)和二氧化碳都是温室气体。沼气可以燃烧来产生负碳足迹的电力，或者产生热能和/或蒸汽，或者因为甲烷的较高全球变暖潜势而燃烧(全球变暖潜势：28-36)。广告是一种权衡；在产生温室气体的同时消耗生物固体。与发电或运输相比，AD是一家规模较小的温室气体生产商。然而，污水处理厂是“(A)被忽视的碳排放源”。最近的一项研究测量了中国大型城市污水处理厂出水中溶解的无机碳对海水的影响。其他人已经展示了减少二氧化碳的实验室和中试规模的广告。渥太华城市污水处理厂(ROPEC)的ADS每年产生约1400万立方米的沼气。该计划旨在评估废弃水泥是否会在AD中沉淀碳酸钙，并减少排放的总二氧化碳气体。从拆除项目中回收的废弃水泥是一种廉价的钙离子和碱度来源。混合废水泥粉对AD无机碳酸盐化学的影响尚未被探索，这是这份规模较小的两年期提案的主题，该提案针对两名PDF、一名硕士、六名合作社和两名暑期学生。在1 L气密式台式反应器上研究固液比、水泥比表面积、停留时间和混合动力学效应。无机碳的固/液气相平衡很难用复杂的AD溶液组成进行精确建模，但简化对无机碳酸盐化学模型的理解可能有助于确定市政AD装置未来的二氧化碳排放目标。USP Technologies的废水处理经验和Fortera USA的碳捕获技术将有助于研究废水泥在ROPEC广告中碳酸钙的沉淀。

Canada's densely populated cities treat their sewage in municipal wastewater treatment plants (WWTPs). Some municipalities use anaerobic digestion (AD) to stabilize sewer sludge. AD off-gas is approximately 65 % CH4 and 35 % CO2 by volume. Both CH4 ("biomethane" or "biogas") and CO2 are greenhouse gases (GHG). Biogas can be burned to produce electric power with a negative carbon footprint, or to produce thermal energy and/or steam, or flared because of the higher global warming potential (GWP) of CH4 (GWP: 28-36). AD is a trade-off; biosolids are consumed while GHGs are generated. AD is a smaller GHG producer than electrical power generation or transportation. WWTPs are, however, "(a)n overlooked source of carbon emissions". One recent study measured the impact of dissolved inorganic carbon from large Chinese municipal WWTP effluents on seawater. Others have demonstrated lab- and pilot-scale ADs with reduced CO2. ADs at the City of Ottawa municipal wastewater plant (ROPEC) produce ~14 million m3/a of biogas.The proposal is to asses if waste cement precipitates calcium carbonate in the AD and reduces the total carbon dioxide gas released. Waste cement recovered from demolition projects is an inexpensive source of calcium ions and alkalinity. The effect of mixing waste cement powder on AD inorganic carbonate chemistry has not been explored, and is the subject of this smaller, two year proposal for two PDFs, one masters, six co-op and two summer students. Solids/liquid ratio, cement surface area, residence time, and mixing dynamics effects would be studied with a 1 L gas-tight benchtop reactor. The inorganic carbon solid/liquid gas equilibria would be difficult to model exactly with the complex AD solution composition, however a simplified understanding of inorganic carbonate chemistry model n AD may be useful for targeting future CO2 release from municipal AD units. Logistical, economical, and geographical aspects of this project will also be modeled and assessed.The wastewater treatment experience of USP Technologies, and the carbon capture skills of Fortera USA would assist with investigating the precipitation of calcium carbonate in ROPECs ADs with waste cement.