Closing the Nutrient Loop-The New Approaches to Recovering Biomass Minerals during the Biorefinery Processes

Abstract

The recovery of plant mineral nutrients from the bio-based value chains is essential for a sustainable, circular bioeconomy, wherein resources are (re)used sustainably. The widest used approach is to recover plant nutrients on the last stage of biomass utilization processes-e.g., from ash, wastewater, or anaerobic digestate. The best approach is to recover mineral nutrients from the initial stages of biomass biorefinery, especially during biomass pre-treatments. Our paper aims to evaluate the nutrient recovery solutions from a trans-sectorial perspective, including biomass processing and the agricultural use of recovered nutrients. Several solutions integrated with the biomass pre-treatment stage, such as leaching/bioleaching, recovery from pre-treatment neoteric solvents, ionic liquids (ILs), and deep eutectic solvents (DESs) or integrated with hydrothermal treatments are discussed. Reducing mineral contents on silicon, phosphorus, and nitrogen biomass before the core biorefinery processes improves processability and yield and reduces corrosion and fouling effects. The recovered minerals are used as bio-based fertilizers or as silica-based plant biostimulants, with economic and environmental benefits.

Keywords: biomass; fertilizer; mineral; pre-treatment; recovery.

Figure 1

Ilustration of the dual goal followed in this work: nutrient recovery solutions during the biorefinery processes and recovered nutrients utilization.

Figure 2

Advantages of the biorefinery approach that recover mineral nutrients as bio-based fertilizers and convert organic carbon into low-volume, high added-value products, including biodegradable bio-based polymers and biofuels that could be used as platform molecules for production of bio-based chemicals.

Figure 3

Potential of the technologies used to reduce hydrogen sulfide and ammonia in the biogas produced from anaerobic digestion to recover nutrients.

Figure 4

The incentives and challenges related to technologies that recover mineral nutrients in the first stages of the biorefinery processes.

Figure 5

The incentives and challenges related to technologies that recover mineral nutrients from the by-products of the biorefinery processes.

Figure 6

The contribution of the mineral nutrients recovered from biomass to carbon farming. Silicon recovered from biomass promote nutrient use efficiency and modulate soil microbiota, including the microorganisms acting for silicate weathering. Recovered microbial strain used for the production of the enzymes acting on biomass could be used to produce microbial plant biostimulants. Biochar promotes the sustainable use of recovered phosphorus.

Figure 7

The digital dimension integrated into the precision agricultural systems supports the application of the recovered nutrients for enhanced soil health.