In-vessel co-composting of horse stable bedding waste and blood meal at different C/N ratios: process evaluation

Abstract

Abattoir blood meal is rich in nitrogen and its potential as a co-composting material for horse stable bedding waste was evaluated at two C/N ratios – 32 (LBM, low blood meal) and 16 (HBM, high blood meal) – to improve the nutrient contents of the final compost. The mix was composted for 7 days in a 10 tonne/day in-vessel composter and cured aerobically. After 56 days of composting, the ammoniacal-N, CO ₂ evolution rate and C/N ratio of both LBM and HBM were within the guideline values; however, delayed decomposition and lower seed germination index were observed with HBM. In addition, HBM resulted in 84% loss of the initial ammoniacal-N. Almost similar organic decompositions, 62.4% and 59.6% with LBM and HBM, respectively, were achieved. However, a stable compost product can be obtained within 6–7 weeks with LBM, whereas>8 weeks were required for HBM composting. Therefore, co-composting at the C/N ratio of 32 is recommended to achieve odour-free and faster composting.

Keywords:

• composting
• in-vessel
• abattoir blood meal
• horse stable bedding waste
• C/N ratio

Acknowledgements

We thank the Hong Kong Environmental Protection Department and Electrical and Mechanical Service Department for permission to use the data generated from the consultancy work for this publication.