Crop residues potential for the bioeconomy is often limited under the basis of avoiding prospective soil organic carbon depletion. However, when processed in the bioeconomy the biomass carbon can be partially recovered in a stabilized degradation-resistant state in the coproducts. This study interlinks the theoretical basis between the coproducts’ characteristics and behavior in soils and the use of soil models to predict the effect of replacing crop residues with bioeconomy coproducts. Stemming from a revision of over 600 datasets we defined conversion coefficients from biomass C to coproduct (Cc) and their inherent recalcitrance in soils (CR) for pyrolysis (Cc: 48%, CR: 95%) and gasification biochar (Cc: 20%, CR: 95%), hydrochar (Cc: 31%, CR: 83%), digestate (Cc: 36%, CR: 68%) and lignocellulosic bioethanol solid (Cc: 44%, CR: 42%) and liquid (Cc: 21%, CR: 46%) coproducts. Different approaches to incorporate stabilized organic matter in soil models were investigated as well as the data requirements of a variety of soil models to set the basis for model adaptation in a dynamic harvest – return of C to explore future scenarios involving the coproducts return as a strategy to increase the bioeconomy feedstock provision while ensuring the maintenance of SOC stocks.

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The production and consumption of oranges generates a large amount of lignocellulosic waste that is deposited in landfills without receiving any type of treatment that allows it to be used as by-products. The objective of the present investigation was to obtain bioalcohol through the saccharification and fermentation of lignocellulosic residues of the peel of the orange (Citrus sinensis). Three (3) different levels of sulfuric acid were used as treatment, to alter the lignocellulosic structure of the biomass, subsequently, a hydrolysis with cellulase enzymes was carried out, analyzing the presence of reducing sugars by spectrophotometry. The fermentation was carried out with two (2) different concentration levels of Sacharomyces cerevisiae yeast, subsequently, it was distilled and the presence of volatile organic compounds was determined by gas chromatography. The reducing sugars present in the highest proportion were: glucose (26.6 ± 0.77 g.L-1) and fructose (21.26 ± 0.51 g. L-1); the volatile organic compound with the highest concentration was ethanol (76.96%) and the index with the highest bioalcohol yield was obtained with the treatment with the highest concentration of sulfuric acid and yeast (12.72 ± 0.65 g. L-1); Orange peels are by-products of vegetable origin that can be used for the production of bioalcohol with percentages of ethanol higher than 76%.

Crop residues potential for the bioeconomy is often limited under the basis of avoiding prospective soil organic carbon depletion. However, when processed in the bioeconomy the biomass carbon can be partially recovered in a stabilized degradation-resistant state in the coproducts. This study interlinks the theoretical basis between the coproducts’ characteristics and behavior in soils and the use of soil models to predict the effect of replacing crop residues with bioeconomy coproducts. Stemming from a revision of over 600 datasets we defined conversion coefficients from biomass C to coproduct (Cc) and their inherent recalcitrance in soils (CR) for pyrolysis (Cc: 48%, CR: 95%) and gasification biochar (Cc: 20%, CR: 95%), hydrochar (Cc: 31%, CR: 83%), digestate (Cc: 36%, CR: 68%) and lignocellulosic bioethanol solid (Cc: 44%, CR: 42%) and liquid (Cc: 21%, CR: 46%) coproducts. Different approaches to incorporate stabilized organic matter in soil models were investigated as well as the data requirements of a variety of soil models to set the basis for model adaptation in a dynamic harvest – return of C to explore future scenarios involving the coproducts return as a strategy to increase the bioeconomy feedstock provision while ensuring the maintenance of SOC sotcks.

The urgency to achieve climate neutrality and limit global warming requires a transition to low fossil carbon use. Crop residues, an abundant source of renewable carbon, remain underutilized, among others due to soil conservation practices. Soil organic carbon (SOC) plays a crucial role in tropical croplands by supporting soil health, nutrient availability, and biogeochemical cycles. The incorporation of exogenous organic matter (EOM) amendments has the potential to enhance carbon storage and fertility. This study conducted in Ecuador, a biodiversity hotspot, aims to identify SOC stock vulnerabilities, estimate SOC storage potential and changes in CO2 fluxes in tropical cropping systems resulting from changes in crop residue harvest for use within the bioeconomy, when a subsequent recalcitrant EOM application is involved. A spatially-explicit modeling framework representing the agricultural area into 15,782 agricultural pedoclimatic units was employed to assess the potential for SOC storage and to quantify resulting CO2 emission changes in tropical cropping systems. Four scenarios were analyzed, all implying the conversion of crop residues into bioeconomy products as well as recalcitrant EOMs. The RothC soil model, adapted to incorporate additional carbon pools for labile (CL) and recalcitrant (CR) fractions, as well as the priming effect, was utilized alongside high-resolution data to evaluate SOC storage potential for each scenario. Baseline SOC stocks ranged from 7.43 to 235 t C ha− 1, with an average of 61.76 t C ha− 1. At the national level, the business-as-usual (BAU) scenario, i.e. crop residues removal, projected a potential 4% increase in SOC stocks by 2040 and a 7% increase by 2070. However, SOC stocks decreased in 79% of the study area. The simulations demonstrated the potential to supply 113 PJ biomass for the bioeconomy without incurring SOC losses in the pyrolysis and gasification scenarios. Harvesting residual biomass with co-product return led to a 19–39% reduction in CO2 emissions over 50 years, depending on the scenario. Sensitivity analyses revealed the priming effect as a particularly sensitive parameter for the results.

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Ecuador se encuentra posicionado como primer exportador de cacao fino de aroma, representando más del 62% de la producción mundial de este fruto, lo que propicia una abundante disponibilidad de residuos valorizables de esta planta. La composición lignocelulósica de estos residuos les confiere la capacidad de ser procesados y transformados a bioetanol. En esta investigación, los residuos de cáscaras, tallos y hojas de cacao fueron acondicionadas (secadas y pulverizadas) y sometidas a un proceso de sacarificación y fermentación simultánea para la producción de bioetanol de segunda generación. La biomasa acondicionada fue sometida a un pretratamiento de hidrólisis alcalina (NaOH al 3%) con explosión de vapor a 121ºC por 90 min a 1 atm. La biomasa hidrolizada se sometió a un proceso de hidrólisis enzimática empleando la enzima celulasa de Aspergillus niger de Sigma Aldrich y se utilizó simultáneamente la levadura Safale S-04 para la fermentación de los azúcares a bioetanol. Las muestras tratadas fueron filtradas y centrifugadas y el contenido de alcohol se cuantificó mediante cromatografía gaseosa. Las condiciones de sacarificación y fermentación simultánea fueron optimizadas mediante un diseño factorial multinivel, empleando la metodología de superficie de respuesta. El diseño incluyó nueve corridas base (todas por triplicado), donde se evaluaron tres concentraciones enzimáticas (5, 15 y 25 FPU/g) para los cinco gramos de carga inicial de material sólido seco (MSS) y tres temperaturas (27, 37 y 47°C). La maximiza producción de bioetanol (0,00240 μL/g) se alcanzó con las condiciones óptimas de 23,5 FPU y 31,7 °C.  Se realizó una última corrida empleando las condiciones óptimas para una mayor carga de biomasa (20 g), alcanzando una concentración máxima de bioetanol de segunda generación de 0,11 mL/L.