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Boron (B) fertilizers are essential for global crop production. Sustainable B use demands a higher efficiency of B fertilizers through controlled B release and an enhanced B recycling from secondary sources, e.g. B-impregnated cellulose fiber insulation (CFI) waste. In this study, thermochemical treatments based on combustion and pyrolysis were investigated for processing CFI waste into a slow-release B fertilizer. Hot-water extractions of obtained materials confirmed that slow-release properties were achieved, and material characterization with XRD, FTIR and 11B-NMR showed that these were largely the result of formation of sparingly soluble Ca–B phases. A seedling toxicity test with fodder rape demonstrated the benefit of this slow-release B in comparison with conventional soluble B to circumvent toxicity, suggesting potential for B application via seed coatings. Finally, a fertilization trial with fodder rape and poppy seed showed that most slow-release B compounds were equally effective as soluble B at recommended B doses, while slow-release B can still benefit from reduced B leaching losses. [Display omitted] • Thermochemical processing of B-rich cellulose fiber insulation (CFI) was tested. • Obtained combustion and pyrolysis products had slow-release B characteristics. • Slow-release B was largely the result of formation of sparingly-soluble Ca–B phases. • B toxicity to plants could be avoided using treated CFI instead of soluble B. • In a plant fertilization trial, treated CFI was equally effective as soluble B. [ABSTRACT FROM AUTHOR]

In a context of climate change and circular economy, it is fundamental to produce animal manure-based fertilizers attractive to farmers who are reluctant to use heterogeneous materials, poorly characterized and with unbalanced nutrient contents, namely N:P ratios different from plant requirements. Hence, the aim of the present study was to assess the potential of different treated and non-treated animal manures to produce tailor-made manure-based fertilizers with known N:P ratios. Seven manures were considered: cattle, caprine and poultry solid manures, two contrasting cattle slurries and two contrasting swine slurries. Slurries were further treated by solid-liquid separation, acidification, and acidification followed by solid-liquid separation. Raw and treated manures were fully characterized to assess the effect of manure type and treatment on their nutrient contents and N:P ratios, to incorporate them in manure-based fertilizers with selected N:P ratio. The present results were essential to support the manure-based fertilizer production and identify which materials could be considered: it appears clearly that the pig slurry with all stages of production and the correspondent liquid fraction cannot be used due to their low nutrients content. It was shown that the solid fractions rich in P and with a N T :N–NH 4 + ratio close to 1 are an excellent material to prepare manure-based fertilizers. Acidification, combined with solid-liquid separation, produced a liquid fraction rich in both N and P and with a N T :P T ratio close to 1, with the additional benefit of a slow N-release material. Some of the manures or sub-products obtained after treatment provided the usual N:P ratio required by farmers and could be used directly as substitutes of mineral fertilizers. Nevertheless, the blending of some of these materials has a stronger potential to the production of specific manure-based fertilizer. • Animal species and manure management influence manure composition and N:P ratio. • Slurry treatment is a good tool to modify N:P ratio of manure. • Combination of raw and/or treated manures allow producing manure based fertilizers. • Manure based fertilizers can have N:P ratio similar to mineral fertilizers.. [ABSTRACT FROM AUTHOR]

The globally growing demand to produce more food with fewer inputs, less energy, and lower greenhouse gas (GHG) emissions challenges current agricultural practices. Recycled fertilizers made of various side streams and types of biomass have been developed mainly to improve nutrient recycling in food systems. However, the knowledge of the impacts of different recycled fertilizers on GHG emissions and energy use is lacking. There is also a need for developing environmental assessment methods for quantifying the impacts of recycling processes, particularly in terms of choosing reasonable methods for co-product allocation. The aims of this study were to address the above mentioned research gaps by i) assessing energy use and GHG emissions of various recycled fertilizers, ii) comparing the recycled fertilizers with mineral fertilizers, and iii) comparing the impacts of using different co-product allocation methods for the recycled fertilizers. Attributional Life Cycle Assessment (LCA) was used for estimating energy use and GHG emissions of recycled fertilizers, including ammonium sulfate, biogas digestate, and meat and bone meal, using kg of nitrogen in the fertilizers as a functional unit. In addition, the energy use and GHG emissions of oat production when using the recycled and mineral fertilizers were quantified. The data were obtained from field experiments, LCA databases, published literature, and fertilizer companies. The life-cycle energy consumption and GHG emissions of recycled fertilizers were found to be lower than that of mineral fertilizer, but also differences between recycled fertilizer products were notable. The biggest differences between fertilizers occurred in manufacturing and transportation. However, this conclusion is highly sensitive to several decisions, such as data sources and LCA methods used. Handling the raw materials of recycled fertilizers as by-products instead of residues adds burdens from primary production to fertilizers. Also handling the materials as waste increases the impacts due to burdens from the recycling process. Since the raw materials of fertilizers have only little economic value, applying economic allocation results to significantly lower impacts than mass allocation. Consequential LCA studies would be needed to improve the understanding of the wider impacts of recycled fertilizers, e.g. considering the benefits of avoided waste management processes. • No statistically significant differences in yields between the fertilizers. • Lower energy use and emissions with recycled than mineral fertilizers. • Notable differences in emissions and energy use between recycled fertilizers. • Effect of data sources and allocation methods were considerable. [ABSTRACT FROM AUTHOR]