Hydrochar produced from dairy manure is a regulated biosolid if being promoted for agricultural applications thus must have the properties that comply with all environmental standards and government regulations,includ...Hydrochar produced from dairy manure is a regulated biosolid if being promoted for agricultural applications thus must have the properties that comply with all environmental standards and government regulations,including the levels of heavy metals(HMs).In this study,systematic research was conducted on HM levels in hydrochar from dairy manure and on the effects of processing conditions,including processing temperature(180–255℃),holding time(30–120 min)and solid content of manure slurry(2%–15%),through a central composite design and statistical analyses.It was found that HMs can be retained in hydrochar,ranging from 40%to 100%.The processing temperature and solid content in the feed were the most influential process parameters that affected HMs retention in hydrochar.Statistical analysis showed that there was no single optimal point to minimize HMs retained in hydrochar,but there were minimization points at given processing time and solid content.Most HMs concentrations were higher in hydrochar than those initially in dairy manure but were greatly below the thresholds as set by the US government regulations.Thus,hydrochar is feasible for use as a phosphorus-enriched organic fertilizer and/or soil amendment for agricultural applications without serious concerns about HMs it might contain.展开更多
基金supported by the hatch projects of USDA National Institute of Food and Agriculture(1012741 and 1019082)Idaho Agricultural Experiment Station(IDA01575 and IDA01604)by a grant from the USDA AFRI Sustainable Agricultural Systems Program(2020-69012-31871).
文摘Hydrochar produced from dairy manure is a regulated biosolid if being promoted for agricultural applications thus must have the properties that comply with all environmental standards and government regulations,including the levels of heavy metals(HMs).In this study,systematic research was conducted on HM levels in hydrochar from dairy manure and on the effects of processing conditions,including processing temperature(180–255℃),holding time(30–120 min)and solid content of manure slurry(2%–15%),through a central composite design and statistical analyses.It was found that HMs can be retained in hydrochar,ranging from 40%to 100%.The processing temperature and solid content in the feed were the most influential process parameters that affected HMs retention in hydrochar.Statistical analysis showed that there was no single optimal point to minimize HMs retained in hydrochar,but there were minimization points at given processing time and solid content.Most HMs concentrations were higher in hydrochar than those initially in dairy manure but were greatly below the thresholds as set by the US government regulations.Thus,hydrochar is feasible for use as a phosphorus-enriched organic fertilizer and/or soil amendment for agricultural applications without serious concerns about HMs it might contain.
