Waste Biopolymers for Eco-Friendly Agriculture and Safe Food Production

Abstract

This work addresses environmental problems connected with biowaste management, the chemical industry, and agriculture. These sectors of human activity cause greenhouse gas (GHG) emissions in the air, climate change, leaching of excess mineral fertilizers applied to soil into ground water, and eutrophication. To mitigate this problem in agriculture, controlled release fertilizers (CRFs) are made by coating mineral fertilizers granules with synthetic polymers produced from the fossil-based chemical industry. This strategy aggravates GHG emission. In the present work, six formulations containing sunflower protein concentrate (SPC) and a new biopolymer (BP) obtained from sunflower oil cake and by hydrolysis of municipal biowaste, respectively, and commercial urea were tested as CRFs for spinach cultivation against the control growing substrate Evergreen TS and commercial Osmocote®. The results show large differences in plants’ nitrate concentration due to the different treatments, although the same nitrogen amount is added to the substrate in all trials. BP is the key component mitigating nitrate accumulation in plants. The plants grown in the substrates containing BP together with SPC and/or urea, although exhibiting relatively high total N uptake (47–52 g kg−1), have significantly lower nitric to total N ratio (9.6–12.0) than that (15.3–16.5) shown by the plants grown in the substrates containing SPC and/or urea, but no BP. The data confirm that all composites containing BP yield the safest crop coupled with high biomass production. Replication of BP effects for the cultivation of different plants will contribute to the development of a biobased chemical industry exploiting biowastes as feedstock.

Biostimulant Effects of Waste Derived Biobased Products in the Cultivation of Ornamental and Food Plants

“…The results of the spinach study [25] showed no statistically significant differences by the substrate treatments compared to the control substrate in leaves and roots weight. The neat SPC and SPC-urea pellets gave significantly the highest leaf chlorophyll content, compared to the control substrate.…”

“…Two other studies carried out for the cultivation of spinach [25] and oil seed rape [10] have disclosed other important effects of SBS, which are associated to the bio-stimulant properties.…”

“…For the spinach studies, composite materials pellets containing D-SBS, sun flower protein concentrate (SPC) and urea were fabricated and tested [25] for their performances as controlled release fertilizers (CRFs). The reason was that urea is a largely used fertilizers worldwide.…”

“…The first study [25] disclosed the D-SBS property to retard the formation of ammonia from urea hydrolysis and enhance the release of organic nitrogen from SPC. This effect was explained to derive from a plausible chemical interaction of D-SBS functional groups with urea and SPC.…”

“…This effect was explained to derive from a plausible chemical interaction of D-SBS functional groups with urea and SPC. As these findings prospected the D-SBS-SPC-urea composites as potential new biobased CRFs, the second study [25] was undertaken to test the above composites in the cultivation of spinach. In this case, a commercial material (Evergreen TS) was used as cultivation substrate.…”