Counting Your Chickens Before They Sequester Carbon and Aid in Water Runoff: Biochar from Poultry Litter
By Justin Beck
It is no mystery that the poultry industry is a massive enterprise that presents a number of challenging impacts on agriculture and the environment. The United Nations Food and Agriculture Organization (FOA) documented in 2002 the world’s population of chickens at more than 16 billion. Two decades later this number is certainly higher, overshooting the human population by more than five times. Being such a large scale sector the byproduct of chicken manure is certainly massive as well. In a 2012 article for the International Biochar Initiative by Kathleen Draper and Thayer Tomlinson titled Poultry Litter Biochar- A US Perspective the authors cite literature that in general, the main use for chicken litter at least in the US is as a fertilizer for hay and cornfields. In the case of birds, the manure is a wetter type as urine and feces are mixed. Furthermore, chicken litter is rarely just the droppings and also includes uneaten feed, feathers, and bedding. Yet poultry litter is high in nutrients including nitrogen and does represent a decent fertilizer.
However, as a fertilizer poultry litter still remains a high-volume, low-value substance which farmers are rarely able to sufficiently capitalize on. Additionally, maintenance of chicken litter requires substantial attentiveness as there are hazards to soil and water systems such as risks of E coli and salmonella. As is the situation for many potential feedstocks, wouldn’t it be something interesting to consider poultry litter (PL) as a feedstock for biochar? Draper and Tomlinson remind us that PL biochar has a number of distinguishing features that make it different than biochar produced from plant materials. These distinct characteristics include a higher nutrient content especially nitrogen and phosphorus. Another difference is a higher cation exchange capacity (CEC) at a lower temperature pyrolysis process. Cation exchange capacity is a matter of chemistry and affects the capability to hold nutrients and decrease nutrient loss due to an ability to hold positive ions. Clay soils and organic matter are higher in CEC properties. PL biochar shares this trait as well. Lower temperature pyrolysis means that the production process utilized to make the biochar can be accomplished at lower temperatures potentially saving energy increasing yields and producing a different type of biochar. A further feature of PL biochar is that it is quite good at sequestering and absorbing metal ions thereby having great potential as a method to aid in cleaning up abandoned mines and other toxic sites. Of course, PL biochar retains much of the other positive aspects that all biochar possesses as well such as being an incredible tool for carbon sequestration in a form very valuable for the plants and environments.
However, it must be noted that while PL biochar is nutrient-richnutrient rich and can represent a beneficial fertilizer amendment, it has a different CO2 sequestering ratio thanthat traditional wood or other plant-based biochar feedstocks. Rimena R. Domingues Et al. from the Department of Soil Science, Universidade Federal de Lavras, UFLA, Lavras, Minas Gerais, Brazil in an article titled Properties of biochar derived from wood and high-nutrient biomasses with the aim of agronomic and environmental benefits writes “Our hypothesis is that nutrient-rich biochars derived from waste have fertilization potential”. Biochars derived from wood or other plant-based materials have better carbon sequestration properties. A comparison from this study of chicken manure biochar with to other feedstocks can be seen in the following table:
|——%——-||__________ g kg -1_____________||_________________ mg kg -1 ________________|
1The contents of P, K, Ca, Mg, Cu, Fe, Mn and Zn were determined in extracts, using the nitric-perchloric protocol as the digestion procedure. 2Total content of B extracted with hot water.
Poultry litter biochar offers a number of benefits as Draper and Tomlinson point out. When PL is converted to biochar the cost of disposal is decreased. This is true in particular in regions where there is an intensity of poultry farming and the environmental impacts are a cause for concern. When pyrolyzed, the material weight of the chicken manure is decreased in half, it becomes much easier to spread and the solubility of the nutrients and potential leaching decreases. Poultry farming, as is the case with other animal-centred agricultural activities poses risks for the spread of “bacterial pathogens such as Escherichia coli O157:H7 (or E. coli), Salmonella, and Listeria monocytogenes on fruit and vegetable commodities consumed raw” as stated by Joshua B. Gurtler Et al. *(ref.1) who further observes that in the U.S. livestock and poultry operations have become more intensive and concentrated in smaller geographic regions which has led to “an abundance of manure, which has been associated with air and water pollution as well as concerns about dissemination of excess nutrients, microbial pathogens, and opportunities for transmission of antibiotic resistance genes”. This agricultural consolidation is most likely not limited to the United States. Pathogens such as Salmonella and E. coli can be deadly and “have been linked to high-profile and lethal foodborne illness outbreaks from consumption of contaminated fresh produce” (Gurtler et al.). Pathogen contamination from poultry litter often takes two forms where both are related to water. Firstly, poultry manure is frequently used as fertilizer for food crops and when coupled with such crops being the ones which we eat raw and pathogens are present in the PL fertilizer then this combination poses a danger. The second primary concern for pathogen transmission via PL is through rainwater runoff which can find its way unintentionally to food crops and water supplies. (K.R. Sistani, American Society of Agronomy, article Broiler Litter Application Method and Runoff Timing Effects on Nutrient and Escherichia coli Losses from Tall Fescue Pasture 2009). Both of these scenarios are exacerbated and accelerated by the intensity and geographical confinement of today’s industrial poultry agriculture. The work done by Gurtler et al. shows that correctly “composted feedstocks that optimize C:N ratios, temperature, and moisture levels can reduce or eliminate bacterial foodborne pathogens present in animal manures to levels recommended by U.S. regulatory agencies and can still be used as a biological soil amendment to grow fruits and vegetables.” This is a promising development. However, pyrolyzing poultry litter to produce biochar goes further. Several studies have shown that when biochar is present in soils there is a marked reduction of the presence of E. coli and Salmonella pathogens. A second study conducted by Gurtler et al., Inactivation of E. coli O157:H7 in Cultivable Soil by Fast and Slow Pyrolysis-Generated Biochar published in Foodborne Pathogens and Disease Vol. 11, No. 3, 2014 demonstrated that soils with biochar, in this case, wood pellet and horse manure feedstock char showed a significant level of inactivity of E.coli over the control soils over a 4-5 week period. A paper by Shoieb Akaram Arief Ismail at the Department of Bioresource Engineering, McGill University, Canada Evaluation of biochar soil amendments in reducing soil and water pollution from pathogens in poultry manure appears to support these findings, the “statistical analysis showed that biochar as soil amendment was significantly more effective (P < 0.0001) in the adsorption of E. coli.”
PL as biochar greatly decreases nutrient runoff, especially when blended with compost. Likewise, PL biochar can aid in increasing agricultural productivity and carbon sequestration. These positive traits are enhanced when completed onsite alongside poultry farming. Lastly, PL biochar could prove to be added economic activity for poultry farmers turning a lower value material such as chicken manure into a higher value material such as biochar.
There are other positive potentials for PL biochar as well. According to Yinghong Yuan et al. from the Institute of Ecology and Environmental Science at the Nanchang Institute of Technology, China in an article titled Is biochar-manure co-compost a better solution for soil health improvement and N2O emissions mitigation? “ Our data demonstrated that the biochar-chicken manure co-compost could substantially reduce soil N2O emissions”. As N2O represents more than 5 percent of greenhouse gas emissions (GHGGhG), we can add one more promising attribute of PL biochar to the list.
ARTi had the opportunity to join in the efforts to work with PL biochar in late 2019. A project in Hawaii required an ARTi Pyrolysis Reactor to effectively process chicken litter for use in biochar production. There were a few special conditions that we needed to address within the scope of this project. First of all, poultry litter is a wet feedstock so our dryer had to be optimized to correctly prepare the PL feedstock for pyrolysis. Secondly, the resulting biochar was intended for soil usage as an amendment so it had to be produced to specifications that suited not just Hawaiian soil, but the soil in that particular region of Hawaii. Furthermore, ARTi sought to address E. coli and Salmonella concerns in the production of this PL biochar at both the input of the process and the output.
*(ref.1) Composting To Inactivate Foodborne Pathogens for Crop Soil Application: A Review.Joshua B. Gurtler Et al., U.S. Department of Agriculture, Journal of Food Protection, Vol. 81
ARTi on site in Hawaii with the Reactor ready to produce PL Biochar
Chicken Litter (PL) feedstock
Chicken litter feedstock being added to the auger system for entrance into the Reactor.
Further augering inside the container unit prepares the feedstock for entering into the pyrolysis Reactor.
Finished, high-quality chicken litter (PL) biochar.