A crop by-product is derived from the production or harvesting of a main crop. These include, for example, cereal straw, beet leaves, potato tops, corn cobs and hay grass. Crop by-products can be used as feed, as a building material, as litter, or as green energy.
Generally, most by-products remain in the field to be re-incorporated into the soil through plowing. When exported from the field, the use that is made of it depends on the type of co-product under consideration. While almost all can be upgraded to energy via biomethanisation, others are better suited for “material” uses. For example, straw is used as an insulation or litter in rearing and the beet tops are used in animal feed. Biorefining is also possible in order to extract platform molecules from this material, but this way of valorisation is still not very widespread.
Land and soil management
The harvesting of by-products must be managed sustainably to ensure the maintenance of soil fertility. This depends on the organic matter (essentially stable carbon), without which one could no longer obtain good yields in the future.
Using by-products in biomethanisation brings two advantages: the production of energy and the return of carbon and nutrients (nitrogen, phosphorus and potassium) to the soil via digestate spreading.