CO2 adsorption on char from rich-protein animal wastes and pure proteins. A comparative study

Carstensen , Hans-Heinrich
18th International Symposium on waste management and sustainable landfilling
Tipo de participación: 
Otros autores: 
J. Ruiz, I. Fonts, N. Gil-Lalaguna, J. Ceamanos, M.B. Murillo, G. Gea
Año : 
S.Margherita di Pula, Cagliari , Italy

Biogas generation through anaerobic digestion (AD) provides an interesting opportunity to valorize animal waste materials through energy production. However, some residues generated in intensive livestock areas, such as meat and bone meal (MBM), cannot be anaerobically digested. A more flexible integrated process is needed to valorize a wider range of residues. Other issues to be addressed in AD are gas upgrading requirements, the increasing costs and the adequate management of the digestate. The high concentration of CO2 in biogas results in a low caloric value, making it mandatory to reduce the CO2 levels. The obtention of low-cost adsorbent materials for CO2 removal, preferably obtained from waste materials, would be beneficial for biogas generation. Char is a potential low-cost adsorbent material. Its composition and quality are strongly dependent on the precursor and its production conditions. Chars from proteins show very different characteristics compared to those obtained from the more commonly studied lignocellulosic residues. More specifically, chars obtained from digested manure and MBM (as rich-protein animal wastes) have a high nitrogen content, which could increase their CO2 adsorption capability if the nitrogen-functional groups contribute to surface basicity. In the current study, the CO2 uptake properties of chars prepared by pyrolysis at three different temperatures of two animal wastes, digested manure and MBM, and two proteins, collagen and soybean protein (considered as representative model compounds of the proteins found in these residues) have been investigated and compared. The CO2 adsorption capacities at room temperature have been measured with a TGA apparatus and the stability and regenerability of all char samples have been determined. The CO2 adsorption capacities of chars from both proteins were found to be very similar (up to 40 mg/g for the chars prepared at 750 ºC). Despite the lower BET surface area of the proteins chars (in the range of 1 m2/g measured with N2 adsorption), their CO2 adsorption capacities was found to be double to those obtained from animal wastes. The preliminary data in this study might be explained with a ultramicroporous texture, but additional work is needed to support this idea.