Biochar Production from Manure and Wet Distillers Grains as an Environmental Management Option

Biochar Production from Manure and Wet Distillers Grains as an Environmental Management Option 2017-11-02T14:04:18+00:00

Shafiqur Rahman, NDSU Department of Ag and Biosystems Engineering

The biomass-derived biochar has shown potential to increase soil properties that are conducive for plant growth with reduced environmental pollution. Therefore, to devise a sustainable farming system in North Dakota (ND) conditions, biochar derived from crop residues and animal manure needs to be investigated. The main goal of the study is to minimize odor and GHG emissions from animal feeding operations through conversion of manure, corn stover and wet distillers grains (WDG) to biochar. Biochar can be used as a soil amendment, can increase water-holding capacity, reduce bulk density, provide additional cation exchange sites, and serve as a source of reduced carbon compounds that may benefit microbial populations, thus ultimately promote plant growth. Similarly, application of biochar in soil can reduce GHG from crop production as well as from feedlot or manure storage.

The specific objectives of this project are to characterize the physico-chemical properties of biochar produced from manure, corn stover, and WDG, and evaluate their effectiveness in mitigating gaseous emission from livestock manure.

WDG samples were collected from Tharaldson Ethanol in Casselton, ND with sizes from 1-3 mm. Dairy and beef feedlot manure was collected from the NDSU Dairy Teaching and Research Unit and NDSU Beef Cattle Research Complex. The corn stover biomass was harvested from NDSU’s experimental field. The samples were air dried to reduce moisture content < 30%. Once the moisture content reached below 30%, the substrate was put through a pyrolysis process to produce biochar. Raw biomass samples and finished biochar were analyzed for different components. Physical and chemical characteristics such as pH, electrical conductivity (EC), bulk density (BD), water holding capacity (WHC), and total organic carbon (TOC) were measured for each biochar derived from four biomasses: corn stover (CS), dried distillers grains soluble (DDGS), dairy manure (DM), and beef feedlot manure (BFM). Biochar characteristics were analyzed in the Waste Management Lab at NDSU and the AgVise laboratories in Northwood, ND.

The BFM had the highest biochar yield (~77%), followed by DM (~ 46%), DDGS (~ 42%), and CS (~ 31 %) after 3 hours of pyrolysis. The BFM also contained the highest ash content and CS the lowest. Conversely, the highest heating values were determined from CS and the lowest from BFM. The highest organic carbon content was obtained with CS (68%) followed by DDGS (63%), DM (44%), and BFM (15.4%) biochars. Scanning electron microscopy images of biochar samples showed consistent aggregates 2-10 µm in diameter, which would be suitable for absorbing pollutant gases and increasing soil water holding capacity. The CS and DDGS biochars showed higher values of total carbon (76%), FC (61%), OC (67%), water holding capacity, and mineral content. The CS and DDGS outperformed the DM and BFM biochars as the best soil amendments. Nitrogen content of corn-based biomass (CS and DDGS) increased with increased pyrolysis times, whereas the manure derived biochars showed a decreasing trend with increased time. The biochar has intrinsic properties for potentially improving soil carbon and soil water loss. Thus, producing biochar from waste through pyrolysis is an effective disposal option for biomass waste generated from farming systems, especially corn stover and WDG due to their high quality biochar.

Due to limited funding, no research has been conducted on the effectiveness of biochar in mitigating gaseous emission from livestock manure. Additional funding is needed for producing a large quantity of biochar, as well as to examine their effectiveness in mitigating some of the environmental concerns both in the laboratory and in the field.