Background Reducing general waste production is widely recognised as an important objective in promoting environmental sustainability. It calls for adapted and sustainable strategies of recycling, re-use or disposal of waste products. Most animal waste – in particular, flesh and hair coming mainly from the leather industry – is disposed of in landfill sites or incinerated, and constitutes a major contamination concern in Europe, in addition to the notable cost of handling and landfill treatment. A possible form of treatment of such wastes is bio-hydrolysis or enzymatic digestion. Bio-hydrolysis transforms the proteins in a solution of amino acids and peptides by enzymatic activity. The enzymes are typically produced by a selected strain of thermoactinomycetes and/or by means of over-expression of pepsin and trypsin in Bacillus subtilis. Laboratory tests and research have indicated the suitability of protease enzymes for hydrolysis of flesh and hair. However, to date, there has been no practical implementation of this process. Objectives The COWtoPLANT project aimed to demonstrate the viability of a new technology based on the bio-hydrolysis of animal hair and skin waste using selected strains of actinomycetes and Bacillus subtilis. It hoped to show the products obtained from this process are suitable for use as fertilisers and pesticides. To this end, the project planned to transform bovine flesh and hair waste using enzymatic digestion. It would then demonstrate that the end product is economically viable for use on a semi-industrial scale as a bio-stimulant and bio-pesticide for plants. The project planned to select representative samples (10kg) of animal waste category 3 from four optimal sources (three national and one international). This waste would be divided up and 70% of it treated by means of hydrolisation using the new bio-technological resources: actinomycete strains and Bacillus subtilis, first in 5 litre bio-reactors of and then applied in bio-reactors of 1 000-1 500 l. The remaining 30% would be treated with alternative environmentally friendly solutions, such as composting and alkaline hydrolysis. The products of the bio-hydrolysis process would be tested as bio-pesticides and fertiliser. The project would then demonstrate the benefit of the use of these products on plants and soil, in particular an increase in plant growth of 20%. This would be achieved first in the laboratory and subsequently in field experiments. Results The COWtoPLANT project defined and implemented a bio-hydrolysis process to degrade category 3 Animal By products (APBs) – mainly horns and skins, including leather, tail and hair. The project experiments helped define optimum conditions for the process, as well as demonstrating its technical and economical viability on an industrial scale. This highly innovative technology results in two final products that stimulate plant growth and improve soil conditions. The experiments at laboratory level showed that the pre-treatment of fresh samples was not necessary, which adds to the economical value/feasibility of the process. The best-adapted types of waste were found to be horns and skins, which were used for the subsequent experiments. The hydrolysis conditions and specifications were then defined and tested in three lab-scale prototype reactors of 5 litres. Different bacteria and process conditions were assayed, allowing the project team to define the optimum hydrolysis procedure. Additional tests were also conducted in order to optimise the various process parameters. Due to a subsequent contamination problem in the reactors, the project team took appropriate measures to find a solution. These led to the definition of a modified procedure: a one-step process using a single reactor and one type of bacteria. The next step was to construct a semi-industrial scale prototype (1 600 litres). After some technical adjustments, the best option was found to be to grow the bacteria (Bacillus sp.) in the bioreactor directly and then add wastes and enzymes to the reactor. The prototype was constructed in a mobile container with a view to conducting demonstration sessions for interested stakeholders such as slaughterhouses. The process at semi-industrial scale was optimised to get a satisfactory waste degradation rate (up to 64%) and a good financial return. The two sub-products obtained are a liquid fraction called hydrolysate that is rich in amino acids and peptides, and a solid fraction, namely partly hydrolysed called pellets. During the entire project period, regular laboratory analysis of the sub-products on various plant species and soils was carried out. These confirmed that these products have a potential value as plant growth stimulant and soil amendment (manly due to their carbon and nitrogen content), and absence of heavy metals and pathogens). Field tests on vegetable crops also showed a positive impact on soil quality and plant growth. For example, the hydrolysate was shown to have a potential value as a bio-stimulant, with an increase in plant growth of up to 30% compared with traditional treatments (acting as metabolic enhancers). Their pesticide effect on specific pathogens was also demonstrated. Finally, a precise cost-benefit analysis was carried out, based on a hypothetical plant able to treat 600kg of APBs per year. Such a plant would be able to recover initial investment and operating costs by three years at the most. The final outcome of the project was a simple bio-hydrolysis procedure for degrading category 3 APBs and for transforming them into potentially valuable agricultural sub-products such as plant stimulants and organic soil amendments. The final degradation rate obtained was 64% and the technology applies to most category 3 APBs (cow horns and skins) but is considered to be also applicable to other types of APBs, such as poultry feathers. The project beneficiary and partners have a strong interest in further improving the technology and its performance in order to reduce production costs and to be able to bring a competitively priced product to market. As the EU regulatory framework for the treatment and disposal of Animal By Products of Category 3 becomes more flexible (latest regulations No 1069/2009 and No 142/2011), the technology has a real application potential.