Resource Utilization of Biogas Waste as Fertilizer in China Needs More Inspections Due to the Risk of Heavy Metals

Abstract

The utilization of livestock waste has attracted increasing attention in recent years. The presence of high levels of heavy metals is a major obstacle to the utilization of biogas as a fertilizer resource. In this study, the heavy metal contents in biogas residue, slurry, and discharged sewage from three representative farms of gooseries, henneries, and dairy farms in the Yangtze River Basin were investigated and assessed. The results demonstrated that heavy metals, including Cd, Mn, As, Cu, Pb, Cr, Zn, etc., could be detected in all biogas residues, with significantly different contents between farm types (p < 0.005). Specifically, biogas residues from the goosery and the dairy farms met “China’s Organic Fertilizer Standards” (COF Standards); however, Cd concentrations in biogas residues from hennery farms exceeded the limits by five times. The concentrations of Cd and Pb in biogas slurries from all of the farms exceeded the limits of the “China Farmland Irrigation Water Quality Standard” (CFIWQ Standard). In particular, the Pb concentrations in biogas slurry from the dairy farms exceeded the limits by 29 times, and the discharged sewage from all three farm types complied with the comprehensive sewage discharge standards in China; however, only that from the goosery farms was suitable for irrigation. Thus, it is recommended to increase the feed selection, biogas engineering, and biological-purification-supporting technology, and to carry out regular sampling inspections of the biogas residue, slurry, and discharged sewage for heavy metals, so that environmental and crop pollution risks can be reduced when they are used as sources of nutrients for eco-friendly agriculture.

Does E-commerce participation increase the use intensity of organic fertilizers in fruit production?–Evidence from China

“…Results of heterogeneous effects estimation. Economic benefits are crucial in promoting the transformation of the production and management methods of fruit farmers [19,52]. The willingness of fruit farmers to change their production and management practices varies depending on the level of participation in e-commerce; consequently, fruit farmers' use intensities of OF vary depending on the level of fruit farmers' participation in e-commerce.…”

Recycling of biogas wastewater to organic fertilizers and influence of organic fertilizers on maize, mung bean growth and yield under the field conditions

“…Based on this regulation these biogas effluent samples did not meet the standards and could not be used directly for irrigation on farming. Therefore, it is necessary to treat pathogenic microorganisms such as E. coli, Coliform in wastewater from biogas digesting systems Chang et al (2022).…”

“…This causes pollution for the receiving water bodies in many localities (Nga et al, 2013;Giang et al, 2021). According to Chang et al (2022), as a byproduct of anaerobic fermentation of animal manure, crop residues, biogas residues can be utilized as high-quality organic fertilizer for farming and vegetable production. Another important thing is that the organic fertilizer can be 2 to 3 times cheaper for the farmer than the fertilizer produced industrially.…”

Cadmium (Cd) Heavy Metal Content in Central Java Shallot Production Center

“…The metal content of Cd in phosphate fertilizer ranges from 0.1 -170 mg kg -1 , SP-36 fertilizer contains 11 mg kg -1 of Cd, and manure contains 0.1 -0.8 mg kg -1 of Cd [24,25]. Biogas waste used for agricultural land also contains Cd; the Cd content in a slurry or biogas liquid waste from cattle farms is 57.69 µg/L and 19.62 µg/L in sewage [22,26]. In addition to fertilizers, various types of pesticides also contain cadmium, both as the main component and as a complementary material, which functions as an adhesive and increases the effectiveness of toxic compounds in pesticides [27].…”