ASSESSMENT OF HEAVY METALS IN HYDROCHAR PRODUCED BY HYDROTHERMAL CARBONIZATION OF DAIRY MANURE

Highlights

● Content of heavy metals in hydrochar varies considerably, from 50% to 100%.

● Concentrations of heavy metals in hydrochar can be higher than those in the dairy manure.

● Concentrations of heavy metals in hydrochar are far below the regulatory level.

Abstract

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 °C), 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.

Graphical abstract

Keywords

heavy metals / dairy manure / hydrochar / hydrothermal carbonization / waste management

References

[1] Heilmann S M, Molde J S, Timler J G, Wood B M, Mikula A L, Vozhdayev G V, Colosky E C, Spokas K A, Valentas K J. Phosphorus reclamation through hydrothermal carbonization of animal manures. Environmental Science & Technology, 2014, 48(17): 10323–10329

[2] He B B, Chen L. Hydrochar as a vehicle for phosphorus cycling from dairy manure to cropland. Global Journal of Engineerring Sciences, 2021, 7(5): GJES.MS.ID.000672

[3] Zhang F, Li Y, Yang M, Li W. Content of heavy metals in animal feeds and manures from farms of different scales in northeast China. International Journal of Environmental Research and Public Health, 2012, 9(8): 2658–2668

[4] Nicholson F A, Chambers B J, Williams J R, Unwin R J. Heavy metal contents of livestock feeds and animal manures in England and Wales. Bioresource Technology, 1999, 70(1): 23–31

[5] Irshad M, Malik A H, Shaukat S, Mushtaq S, Ashraf M. Characterization of heavy metals in livestock manures. Polish Journal of Environmental Studies, 2013, 22(4): 1257–1262

[6] Bouwman L, Goldewijk K K, Van Der Hoek K W, Beusen A H W, Van Vuuren D P, Willems J, Rufino M C, Stehfest E. Exploring global changes in nitrogen and phosphorus cycles in agriculture induced by livestock production over the 1900–2050 period. Proceedings of the National Academy of Sciences of the United States of America, 2013, 110(52): 20882–20887

[7] Brands E. Siting restrictions and proximity of Concentrated Animal Feeding Operations to surface water. Environmental Science & Policy, 2014, 38: 245–253

[8] Vadas P A, Powell J M. Monitoring nutrient loss in runoff from dairy cattle lots. Agriculture, Ecosystems & Environment, 2013, 181: 127–133

[9] Liu R, Wang J, Shi J, Chen Y, Sun C, Zhang P, Shen Z. Runoff characteristics and nutrient loss mechanism from plain farmland under simulated rainfall conditions. Science of the Total Environment, 2014, 468–469: 1069–1077

[10] Lang Q, Chen M, Guo Y, Liu Z, Gai C. Effect of hydrothermal carbonization on heavy metals in swine manure: speciation, bioavailability and environmental risk. Journal of Environmental Management, 2019, 234: 97–103

[11] Anjum R, Grohmann E, Krakat N. Anaerobic digestion of nitrogen rich poultry manure: impact of thermophilic biogas process on metal release and microbial resistances. Chemosphere, 2017, 168: 1637–1647

[12] Lang Q, Guo Y, Zheng Q, Liu Z, Gai C. Co-hydrothermal carbonization of lignocellulosic biomass and swine manure: hydrochar properties and heavy metal transformation behavior. Bioresource Technology, 2018, 266: 242–248

[13] United States Environmental Protection Agency (US EPA). A Plain English Guide to the EPA Part 503 Biosolids Rule. US EPA, 1994. Available at US EPA website on May 11, 2023

[14] Rajkumar M, Ma Y, Freitas H. Improvement of Ni phytostabilization by inoculation of Ni resistant Bacillus megaterium SR28C. Journal of Environmental Management, 2013, 128: 973–980

[15] Lehmann J, Joseph S. Biochar for Environmental Management—Science, Technology and Implementation. 2nd ed. New York: Routledge, Taylro & Grancis Group, 2015

[16] Liu Z, Quek A, Kent Hoekman S, Srinivasan M P, Balasubramanian R. Thermogravimetric investigation of hydrochar-lignite co-combustion. Bioresource Technology, 2012, 123: 646–652

[17] Githinji L. Effect of biochar application rate on soil physical and hydraulic properties of a sandy loam. Archives of Agronomy and Soil Science, 2014, 60(4): 457–470

[18] Cao X, Ma L, Liang Y, Gao B, Harris W. Simultaneous immobilization of lead and atrazine in contaminated soils using dairy-manure biochar. Environmental Science & Technology, 2011, 45(11): 4884–4889

[19] Lee J W, Hawkins B, Day D M, Reicosky D C. Sustainability: the capacity of smokeless biomass pyrolysis for energy production, global carbon capture and sequestration. Energy & Environmental Science, 2010, 3(11): 1695–1705

[20] United States Environmental Protection Agency (US EPA). Use of Composting for Biosolids Management. US EPA, 2022. Available at US EPA website on May 11, 2023

[21] Reza M T, Lynam J G, Uddin M H, Coronella C J. Hydrothermal carbonization: fate of inorganics. Biomass and Bioenergy, 2013, 49: 86–94

[22] Wang X, Li C, Zhang B, Lin J, Chi Q, Wang Y. Migration and risk assessment of heavy metals in sewage sludge during hydrothermal treatment combined with pyrolysis. Bioresource Technology, 2016, 221: 560–567

[23] Xu X, Jiang E. Treatment of urban sludge by hydrothermal carbonization. Bioresource Technology, 2017, 238: 182–187

[24] Fu H, Wang B, Wang H, Liu H, Xie H, Han L, Wang N, Sun L, Feng Y, Xue L. Assessment of livestock manure-derived hydrochar as cleaner products: insights into basic properties, nutrient composition, and heavy metal content. Journal of Cleaner Production, 2022, 330: 129820

[25] Song C, Yuan W, Shan S, Ma Q, Zhang H, Wang X, Niazi N K, Wang H. Changes of nutrients and potentially toxic elements during hydrothermal carbonization of pig manure. Chemosphere, 2020, 243: 125331

[26] Chen G, Wang J, Yu F, Wang X, Xiao H, Yan B, Cui X. A review on the production of P-enriched hydro/bio-char from solid waste: transformation of P and applications of hydro/bio-char. Chemosphere, 2022, 301: 134646

[27] Wang H, Yang Z, Li X, Liu Y. Distribution and transformation behaviors of heavy metals and phosphorus during hydrothermal carbonization of sewage sludge. Environmental Science and Pollution Research International, 2020, 27(14): 17109–17122

[28] US Congress. Resource Conservation and Recovery Act. Public Law 94–580. US Congress, 1976. Available at US government information website on May 11, 2023

[29] American Society of Agricultural and Biological Engineers (ASABE). ANSI/ASAE S358.3 MAY2012 (R2021). Moisture measurement—Forages. St. Joseph, Ml: ASABE, 2021

[30] Anderson K, Farwell G, Gibson P, Ricks B. Total recoverable elements in biological, plant, and animal tissue and feed samples. Standard Methods SMM.57.070.04. Moscow: Analytical Sciences Laboratory, University of Idaho, 2017

[31] He B B. Batch process operational effects on phosphorus attainment in hydrochar produced by hydrothermal carbonization of dairy manure. Journal of the American Society of Agricultural and Biological Engineers, 2023, 66(1): 141–148

Acknowledgements

This work was in part financially supported by the hatch projects of USDA National Institute of Food and Agriculture (1012741 and 1019082) and Idaho Agricultural Experiment Station (IDA01575 and IDA01604), and by a grant from the USDA AFRI Sustainable Agricultural Systems Program (2020-69012-31871). Sincere thanks are extended to Chad Dunkel (Department of Chemical and Biological Engineering, University of Idaho) and Kevin Kruger (Twin Falls Research and Extension Center, University of Idaho) for their assistance in sample collection and laboratory preparation in this study.

Compliance with ethics guidelines

B. Brian He, Zheting Bi, and Lide Chen declare that they have no conflicts of interest or financial conflicts to disclose. This article does not contain any studies with human or animal subjects performed by any of the authors.

RIGHTS & PERMISSIONS

The Author(s) 2023. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)