Solid wastes from the meat industry are produced in large amounts resulting in a negative impact on the environment if not properly treated. Due to their high content of proteins and fats, these residues are excellent substrates for anaerobic digestion which holds high potential for methane yield. However, possible toxic compounds may be formed during its biodegradation with a consequent failure of the process under long-term operation. The anaerobic co-digestion of such residues with other co-substrates as those generated in agricultural activities has been proposed as a good alternative to overcome these problems. Nevertheless, today there is very little knowledge to assess on mixture interactions connected to wastes composition, biodegradability, and the kinetics of the anaerobic process when complex materials are utilized in ternary and quaternary mixture, specifically when co-digesting solid cattle slaughterhouse waste with agrowaste. It is therefore important to select the right combination of substrates and ratios to obtain synergy instead of antagonism in those mixtures. This chapter aims to provide an overview of the anaerobic digestion of solid slaughterhouse waste and agrowaste, as well as the influence of mixture interactions on its biodegradation.Keywords: "growaste, anaerobic digestion, co-digestion, synergy, slaughterhouse waste © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. . IntroductionThe agriculture sector belongs to one of the most important human activities, but at the same time, it is considered as one of the most residue-producing sector in the world. Farmer activities have a huge impact on the environment, and moreover, industries related to agriculture, such as the meat processing industry, generate a large amount of high-strength residues. Due to the growing demand of meat in the world, the amount of organic solid wastes from meat producing industries is increasing every day. There are several attempts to improve the biodegradation of such residues, such as the anaerobic process, the preferred technology to diminish the organic load with an adequate efficiency [ -]. It is well known that anaerobic digestion "D provides both environmental solutions and renewable energy production in rural areas, in most cases, with the corresponding autonomy."ecause of the high content of proteins and fats, slaughterhouse residues are holding high biogas potential and hence are interesting for the anaerobic digestion process. However, potential inhibitory compounds can be formed during the degradation of proteins and lipids, which make this process sensitive and prone to fail [ -]. " possible way to overcome these problems is the co-digestion with carbon-rich co-substrates, i.e., a mixture of agrowastes with low protein/lipid content. This will lead ...