From waste to worth: Harnessing residual biomass to boost soil quality and carbon sequestration

One of the major global challenges of agriculture is to meet the increasing food demand while combating soil degradation, which affects over 40% of arable lands. This degradation escalates reliance on mineral fertilizers and heightens the risk of environmental deterioration. The valorization of agricultural, livestock, and forestry wastes through their conversion into organic amendments emerges as a pivotal strategy to restore soil health, enhance agricultural productivity, and manage waste efficiently. This aligns with the EU Soil Mission’s goal to ensure that at least 75% of soils are healthy and functional under the “A Pact for Soil in Europe” initiative.

This contribution will show how applying organic residues from agriculture and livestock, processed into green compost, digestate, or biochar, can serve as effective organic amendments. The use of olive mill waste biochar in deficit-irrigated olive crops led to increased plant photosynthesis rates, water use efficiency, and Carbon sequestration, significantly boosting stable soil carbon content. Additionally, the presentation will highlight the effects of applying green compost, and biochar, both individually and in combination with liquid amendments (compost tea, cow manure digestate and cow slurry), on acidic and alkaline soils. The results indicated that biochar significantly enhanced carbon stability (up to 9 times). A high dose of compost tea negatively impacted plant germination and growth, whereas a mix of compost and biochar improved water retention and productivity in both soil types. These findings underline the importance of selecting appropriate organic amendments to optimize soil health and agricultural performance. They also emphasize the crucial role of waste valorization from agricultural and livestock sectors in promoting sustainable farming practices, improving soil resilience, and contributing to carbon sequestration, crucial in advancing towards a sustainable agriculture.

Acknowledgments: Funding for the AGRORES and RES2SOIL projects (PID2021-126349OB-C21 and PID2021-126349OB-C22) by MCIN/AEI/ 10.13039/501100011033 is gratefully acknowledged. Additional support from the Junta de Andalucía, the EU (EAFRD), and the AEI association through Resioliva Operational Group (File No. GOPO-CO-23-0004) is also appreciated.