Humusica 2, article 16: Techno humus systems and recycling of waste

Techno humus systems correspond to man-made topsoils under prominent man influence. They may be purposely conceived for supporting agricultural activities or dumping of waste products, sometimes abandoned to an unknown evolution. Both categories needed a more scientific frame. This is the reason we classified them as morpho-functional humus systems. Improving agricultural soils with organic waste products is an ancestral practice. We present four examples of techno humus systems purposely created for supporting plant growth. Considering a simple home-made composting pile, we give a few basic notions about the biological functioning of these artificial humus systems. Humipedon functioning and structuration are similar to those observed in natural humus systems. Using even animal manure, we illustrate how to manage larger compost piles of waste for application in farming areas. Composting waste that contains animal proteins needs a more careful measurement of the temperature of the pile and a longer period of elevated temperature in the core of the pile. Mulching of pruning residues is presented in a large urban context. The use of mulch must take into account quality and composition of woody material. The lack of nutrients in some residues has to be compensated by a moderate use of appropriate mineral fertilizers. Municipal solid waste, anaerobic digestion residues (grape remains) and spent mushroom compost, eventually mixed with mineral fertilizers, have been tested in horticulture. Benefits and drawbacks are listed for each experiment, with the evolution of carbon storage along 8 years of horticultural practice. Finally, we present an example of “dump” humus system. Mine tailing wastes represent a huge problem in many countries. Pointing on their microbial activity, we show that they must be seen as manageable living humipedons, not as piles of inert rocky material.