GO Ash4Soil: Productive improvement of soils, agricultural crops and forest plantations through an amendment obtained from the valorisation of biomass ash

Europe is facing a major challenge in terms of sustainability in agricultural and forestry systems, especially in relation to the use of inputs that improve soil health and fertility. A representative example is liming, a very important practice in acidic soils (pH<5.5 for most of the year), where acidity significantly limits production. Spain has approximately 40% of acidic soils, where liming is essential to improve fertility, and must be supplemented with the addition of fertilizers that are not in sufficient quantity to cover the needs of crops (macronutrients N, P and K). The liming materials used in Spain come from the east and south of the peninsula (Tarragona, Barcelona, Almería) and require a large volume of non-renewable energy to transport them to the Spanish areas with acid pH, such as Extremadura, Castilla y León and Galicia. The environmental costs derived from this transport could be solved through the use of calcium-rich waste, such as ash, promoting the bioeconomy and the circular economy. Ash from the burning of forest waste for energy production currently constitutes an organic waste whose current destination is landfill. However, its liming capacity is notable, since the main component of ash is calcium, a liming material par excellence. Specifically, in Galicia there is a large availability of this waste, so business models associated with its reuse can be considered. But the soil microbiota, the true support of the vitality and health of the soil, and crops also need nutrients supplied in the form of fertilisation. Mineral fertilisers are widely used in the world for this purpose, especially those that supply phosphorus and nitrogen. An interesting alternative to the use of mineral fertilizers is the use of slurry, the main waste from livestock farming, which can be recovered and used as a high-quality nitrogen fertilizer. This waste is widely available in livestock farming areas in Galicia, Extremadura and Castilla y León.