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Innovative approaches to turn agricultural waste into ecological and economic assets

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Agricultural waste helps in the transition to a new zero waste economy

European researchers and Asian partner organisations have worked alongside stakeholders to bring the circular economy to the agricultural sector. This means the creation of new technologies and biomaterials, while promoting the prevention of waste, its reuse and recycling.

Climate Change and Environment

The dawning of the zero waste society means a much greater focus on waste prevention. This can be achieved by redesigning resource lifecycles to encourage responsible production, consumption, reuse, and the recovery of products and packaging. The goal is for no waste materials to be landfilled, incinerated, or discharged to the ocean or air. The EU-funded NoAW project addressed this challenge by developing innovative solutions for converting agricultural by-products like straw, manure, and vineyard waste into valuable resources. “We converted previously unused agricultural waste into bioenergy and biobased products with direct benefits for the environment, economy, and consumer,” states project coordinator Nathalie Gontard.

New tools for new technologies

Consortium members created with stakeholders, innovative eco-design tools to assess optimal agricultural waste management at the regional scale, with the aid of the NoAW Knowledge Exchange Stakeholders Platform, and applied them to case studies. They also developed technologies to replace petroleum-based plastic production and for bioenergy, biofertiliser, biopackaging, as well as biomolecules and building blocks to replace a significant range of non-renewable oil-based equivalents. In addition, NoAW enhanced anaerobic digestion (AD), a mature waste conversion technology, into a two-step process. Project partners first conducted a wet explosion (WEx) of agricultural waste to pretreat the material before converting lignin into its components (cellulose, hemicellulose and lignin). The WEx involved a thermochemical pretreatment with the addition of oxygen and explosive decompression, which can be adjusted to subsequent biocatalytic and microbial processes.

Reduction in CO2

The two-step AD process produced biogas comprising hydrogen, methane and CO2, as well as volatile fatty acids (VFAs) and nutrient rich digestate fertiliser. Researchers then used microbial electrosynthesis to upgrade the AD biogas into biomethane and biohythane for use as an automotive biofuel or to be injected into the natural gas grid. Project partners also improved the microbial and chemical quality of the digestate to ensure its safe use as a fertiliser, thereby returning nutrients to land where manure potential is poor. Using AD to treat manure, nitrogen availability is increased by 5-20 %, which could reduce mineral fertiliser use by 10 %, a decrease of 3-5 million tonnes of CO2 per year. Researchers conducted the fermentation of the VFAs from the two step AD process using bacteria to produce naturally biodegradable and recyclable polyester polyhydroxyalkanoates (PHAs), which can partially replace oil-based plastics. The scientists improved the PHAs’ properties using composites with lignocellulosic fillers and active materials with antioxidants from winery waste. According to Gontard: “By providing a sustainable alternative to conventional plastic for use in packaging and other applications, NoAW can help European industry and society achieve EU targets for renewable energy and materials, as well as reduce global warming and persistent pollution from plastic.” Furthermore, collaboration with project partners from China, Hong Kong, Taiwan, and an Asian mirror platform has extended the projects reach beyond the EU. This will provide a new vision aligned with the principles of the circular economy that can inspire future generations of farmers, agronomists, and food actors to reshape the meaning and use of crops. “We have developed key, breakthrough collaborative synergies, which we hope will be exploited further within the framework of the next EU-China collaborative project proposal under Horizon Europe,” Gontard concludes.

Keywords

NoAW, agricultural waste, plastic, circular economy, AD process, PHA, anaerobic digestion, polyhydroxyalkanoates, volatile fatty acids, zero waste

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