Co-products from a biofuel production chain in crop disease management: A review

The economic importance of biofuel industrial production chains will increase in the coming years and will be a promising source of co-products that are useful for sustainable farming systems. However, the use of co-products that are obtained from the biofuel production chains, especially for crop disease management, is an under-explored area in the research community. The liquid and solid co-products that are related to the biofuel outputs of particular interest in crop protection are 1) oil-less seed meals and glycerin derived from the biodiesel chain, 2) steam-exploded liquid waste derived from a 2nd-generation bioethanol chain, and 3) charcoal (bio-char) obtained from the pyrolysis of plant biomass. It is interesting to include the suppressive composts that are obtained by composting agricultural waste and the exhausted biomasses originating from the different biofuel chains. This overview summarizes the nature, the effects, the mechanisms, the possible applications, and the use in crop protection of the most important solid and liquid co-products that are obtained from industrial processes, focusing on 2nd-generation biofuel outputs to control economically important plant diseases that are caused by soil-borne pathogens. The aim of this work is to review the available studies on the employment perspectives of biofuel chain co-products in crop protection by distinguishing the two concepts that are most important in sustainable farming systems: 1) the possible effects of these organic inputs in terms of interaction with beneficial soil microbial populations and 2) the possible relationships of these organic inputs in terms of interaction with the physiological and ecological processes of the crop-pathogen systems. This distinction will permit a good definition of the potential advantages of biofuel chain co-products with respect to the traditional organic amendments that are usually used in crop protection. It is evident from this review that biofuel chain co-products have great potential but sometimes give inconsistent disease control, which limits their use in crop protection. There is no doubt that the benefits of biofuel chain co-products outweigh their drawbacks, but the impact of this approach on pathogen populations and disease suppression is often unpredictable.