*note: due to a technical glitch, the audio at the beginning of this recorded presentation was not captured. Please accept our apologies.
Purpose
Sustainable intensification of agriculture aims to boost food production while minimizing environmental damage. Current farming practices often lead to inefficient nutrient cycling, contributing significantly to water and air pollution. Agricultural runoff, especially from livestock systems, introduces pollutants like nitrogen and phosphorus into waterways, causing issues like eutrophication and anoxic conditions, which harm aquatic ecosystems. Agricultural emissions also account for a large portion of global methane and nitrous oxide emissions. To meet increasing food demands, farms have intensified production, further worsening environmental impacts due to increased use of nutrients and feed. Addressing these issues requires innovative solutions that can balance productivity and sustainability.
One promising approach is pyrolysis, which thermochemically converts biomass into syngas, bio-oils, and biochar. While syngas and bio-oils are used for energy, biochar can improve soil health, reduce nutrient leaching, and sequester carbon. Research shows biochar can effectively retain nitrogen and phosphorus, making it a potential candidate for use in wastewater treatment and as a manure storage cover to reduce emissions. Additionally, converting manure into biochar could improve transport logistics by densifying nutrients, making it more economically feasible for farms to manage nutrient surpluses. However, more research is needed to expand biochar’s use beyond fields and into broader agricultural applications to fully realize its environmental and economic benefits.
What Did We Do?
A pilot pyrolysis system, the Pilot Activator from ARTi (Figure 1), was installed at UW-Platteville to process biomass under controlled conditions, allowing for plot-scale studies on biochar applications in agriculture. Biochar was made from separated manure solids at 400 and 600 degrees C at the pilot system at UW-Platteville. Additional biochar was produced from wood chips from a full-scale system integrated at a site in Wisconsin. Biochar was applied to plot trials (Figure 2) to assess the impacts to yield, soil nutrient cycling, crop nutrient uptake, and greenhouse gas and ammonia emissions with varying manure and biochar applications. The trials have been divided into two concurrent field trials to assess various aspects of biochar incorporation practices into livestock-cropping systems.
Trial 1 – Separated manure solids biochar as a phosphorus fertilizer
The main objective in this study is to examine the impacts of applying separated manure solids versus biochar made from separated manure solids to assess the impact of pyrolysis on the phosphorus availability. Separated manure solids (10.9 tons/acre) and biochar produced from separated manure solids at 400 and 600 degrees C was applied based on phosphorus demands for corn silage and supplemented with urea after biochar application, incorporated into soil, to meet recommended nitrogen application. Crop yield and soil impact were assessed at the end of the trial.
Trial 2 – Biochar amended slurry manure
The main objective in this second trial is to examine the impacts of integrating biochar with slurry manure applications to assess the impacts to corn silage production systems, ammonia and greenhouse gas emissions. Slurry manure was applied at a rate of 10,000 gal/acre and biochar was applied and incorporated. Treatments included manure control, biochar made from separated solids at 400 and 600 degrees C at 1 ton/acre, wood biochar made at 600 degrees C applied at 1, 2,5, 5 and 10 tons per acre, and a control that received no manure or biochar. Plots were assessed for the impact to soil nutrient concentration, corn silage yield, nutrient use efficiency, and emissions (measured using a Gasmet Technologies Inc. model DX4015 Portable Fourier-transform infrared spectroscopy (FTIR) Multi-component Gas Analyzer).
For each trial, soil sampling and analysis was conducted prior to amendment application, post application, and post-harvest. Corn silage was grown in all trials and harvested and weighed at the end of each trial. Biochar was always applied to the soil following manure application and then incorporated within 24 hours. At the end of the season, plant tissue samples were collected, dried, and analyzed for nutrient uptake to be used to calculate nutrient use efficiency.
What Have We Learned?
Data is currently being analyzed from year one of the field trial to assess the impacts with biochar application. Thus far, we have determined little difference in yields in the treatments for both trials. This indicates for trial 1 that phosphorus availability from biochar produced from separated manure solids is similar to that of the separated solids. Additional data analysis will allow for comparison of emissions and impacts to soil nutrients.
Future Plans
Additional data analysis will be completed this spring to determine statistical differences in treatments for the parameters measured. In addition, as biochar is thought to have greater impacts in future cropping years, the fields will have manure applied in year 2 and the plots analyzed again for the same impacts as year one to determine further impacts as biochar ages in the soil.
Authors
Presenting and Corresponding author
Rebecca A. Larson, Professor, Nelson Institute for Environmental Studies, University of Wisconsin-Madison, rebecca.larson@wisc.edu
Additional author(s)
Tyler Liskow, Engineer, Nelson Institute for Environmental Studies, University of Wisconsin-Madison; Brian Langolf, Researcher, Nelson Institute for Environmental Studies, University of Wisconsin-Madison; and Joseph Sanford, Assistant Professor, University of Wisconsin-Platteville
Additional Information
Biochar Production through Slow Pyrolysis of Animal Manure
Acknowledgements
This material is based on work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, NLGCA under award number 2022-70001-37309.
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
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