Location: Commodity Utilization Research2011 Annual Report
1a. Objectives (from AD-416)
The research objectives are to develop slow pyrolysis (or torrefaction) and activation processes to convert agricultural feedstock (crop residues, manures, processing wastes, and biorefinery by-products) into: (1) chars that can be used as industrial adsorbents; (2) chars that can be used as soil amendments which improve soil quality, water quality, and sequester carbon; (3) chars that can be used as energy sources (in combustion or gasification); and (4) bio-gas and bio-oil co-products that provide some of the heat and power requirements of the pyrolysis/torrefaction/activation operations and possibly excess heat/power for sale.
1b. Approach (from AD-416)
The approach will be to take agricultural feedstocks (crop residues, animal manure, and biorefinery waste) and heat them under different gas atmospheres to a set temperature. In order to create chars for target applications, the temperature, heating time, and gas atmosphere will be varied, as well as performing pretreatment (before heating) or post treatment of the chars to obtain desired properties. The products will be tested for target applications in our laboratories and also with collaborators with expertise in ammonia adsorption, soil amendments, bio-oil production, and large-scale pyrolysis.
3. Progress Report
Considerable progress has been made on the process for developing of advanced materials to remove (or stabilize) pollutants in soil, water, and air or to serve as an additive to soil. Future work will also investigate the possibility of using these materials as fuels. Biochars (plant or animal waste heated without air) were produced by heating cotton seed hulls, almond shells, biorefinery waste lignin (woody byproduct), and chicken manure in a hot oven to several different temperatures. They were kept in the oven for 1 to 4 hours. After cooling, these biochars were washed in water or left un-washed and inspected both physically and chemically. We found that the materials kept their density unless the oven was very hot (800° Centigrade). In the hotter oven small channels (pores) developed in the chars which increased the active surface area. However, this was not true for all the starting materials. For example, almond shell char did not develop pores even at 800°. If steam was added to the oven above the chars, the active surface area increased in all cases. Previous studies had shown that mercury could be removed from air using biochars made from chicken and turkey manure. In new studies, we replaced the air with a gas similar to the one seen in exhausts from coal-fired power plants. The un-washed biochars made from chicken manure worked very well and removed almost all the mercury form the gas. Biochars made from turkey manure also worked well if it was washed. Washing adds additional cost to the process. A manuscript was published with the results. Biochars made at 350° from cotton seed hulls was effective in removing copper, nickel, cadmium, and lead from a water and soil system. Later studies investigated the importance of chemical composition and function of the surface of the biochars; it was noted that the chars made at low temperature contained more oxygen groups, which are known to attract metal contaminants. Biochar made from chicken manure was also effective in removing metals (except nickel) from the same type of system. Experiments with different types of soils and natural organic matter (found in many soils) showed that the natural organic matter prevented some of the metals to adsorb to the chars. Multiple manuscripts were published with the results. Work with collaborations showed that biochars left from a process to make bio-oils (by very fast heating of powdered biomass) could later be slowly heated in the presence of steam to make biochars that were better (on average) at removing metals, such as copper, nickel, cadmium, and zinc from water, than the starting biochars. Using electron microscopy, we were able to show that pores were made by the steam and this resulted in more surface area per weight of biochar.
1. Biochars from chicken manure can remove mercury from power plant flue gas. Mercury is a contaminant in power plant flue gas if mercury-containing coal is burned. Biochars made by ARS researchers, in the Commodity Utilization Research Unit, in New Orleans, Louisiana, from chicken manure in laboratory-scale equipment were tested to see how well they could remove mercury from a typical flue gas. The results showed that the biochars worked better if they were not washed after the chars were made. This is positive news for the chicken industry as their low-value waste could be used to clean up environmental pollutants.
2. Biochar production process temperature affect potential for using them as soil conditioners. Biochars are being studied by many for use as a soil amendment and general soil conditioner. ARS researchers, in the Commodity Utilization Research Unit, in New Orleans, Louisiana, created biochars from cotton seed hulls at five different temperatures (200 to 800° Centigrade) and then determined how well the biochars could bind heavy metals in soils. The results showed that biochar amendments to a sandy soil was most effective when the biochar had been made at 350°. As much as 90% of the metals were immobilized by the biochar. This is positive news as biochar now can be seen as a soil conditioner for metal contaminated soil.
Uchimiya, M., Wartelle, L.H., Lima, I.M., Klasson, K.T. 2010. Sorption of deisopropylatrazine on broiler litter biochars. Journal of Agricultural and Food Chemistry. 58(23):12350-12356.