Long-term performance of three mesophilic anaerobic digesters to convert animal and agro-industrial wastes into organic fertilizer

Authors: ZHANG, XIAOQIAN - China Agricultural University; LOPES, IGOR - Purdue University; NI, JI-QIN - Purdue University; YUAN, YONGPING - Environmental Protection Agency (EPA); Huang, Chi Hua; Smith, Douglas; CHAUBEY, INDRAJEET - Purdue University; WU, SHUBIAO - Aarhus University

Submitted to: Journal of Cleaner Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2021
Publication Date: 4/26/2021
Citation: Zhang, X., Lopes, I.M., Ni, J., Yuan, Y., Huang, C., Smith, D.R., Chaubey, I., Wu, S. 2021. Long-term performance of three mesophilic anaerobic digesters to convert animal and agro-industrial wastes into organic fertilizer. Agricultural Water Management. 307. Article 127271. https://doi.org/10.1016/j.jclepro.2021.127271.
DOI: https://doi.org/10.1016/j.jclepro.2021.127271

Interpretive Summary: Anaerobic digesters are one method animal feeding operations can manage manure while producing energy and reducing the overall volume of waste. There is little information regarding the land application of digester effluent compared to manure that managers already know how to handle. This research was conducted to evaluate the implications of land applying digester effluent compared to the manure used to feed the digesters. Treatments were manure (influent) and effluent from two digesters located on dairies, commercial fertilizer and an unfertilized control. Rainfall was simulated on plots the day after application and soil samples were collected for the duration of the corn growing season (5 months). Phosphorus runoff was greatest from the two dairy digester effluent treatments, with soluble phosphorus accounting for a majority of the phosphorus lost from these treatments. It appears the reduction in particle size during the anaerobic digestion clogged soil pores and resulted in runoff occurring quicker than in the other treatments. Conversely, soil phosphorus levels were greater from the manure and commercial fertilizer treatments up to 5 months following fertilization. This work provides information to producers using this technology for manure management about how the digester effluent impacts water and soil water upon land application. It will help these producers and policy makers in fine-tuning how to minimize water quality degradation with greater adoption of anaerobic digester technology.

Technical Abstract: The agricultural application of raw manure from livestock and its anaerobic digested product, i.e., liquid effluent, could cause nutrient losses to surface waters and be a serious threat to water quality. The objective of this study was to compare the impacts of fertilization with chemical fertilizer, dairy manure, and digestate on the runoff, sediment, and phosphorus (P) losses, as well as soil P status. A field experiment was carried out using six treatments (unfertilized control, chemical fertilizer, raw dairy manure from two digesters, and their corresponding liquid effluents). Simulated rainfall was applied within 24 - h of fertilization to create a worst-case scenario. Fertilization effects were evaluated by measuring runoff properties (runoff volume, sediment loss and P concentrations in runoff water), and soil P contents in 0-5 cm and 5-20 cm depths. Results showed that under a rainfall event immediately after fertilizer applications, treatments of liquid effluent from digester 1 and digester 2 resulted in a 1.6- and 24.7-fold increase in cumulative total P losses relative to raw manure, dominated by the dissolved reactive P fraction. However, raw manure-amended plots had greater soil profile P than liquid effluent treatments. The findings can be useful in managing raw manure and anaerobic digestate and estimating the environmental risk of nutrients derived from manure and digestate applications.