Maria D. Sanchez-Garcia

Biochar accelerates organic matter degradation and enhances N mineralisation during composting of poultry manure without a relevant impact on gas emissions

A composting study was performed to assess the impact of biochar addition to a mixture of poultry manure and barley straw. Two treatments: control (78% poultry manure + 22% barley straw, dry weight) and the same mixture amended with biochar (3% dry weight), were composted in duplicated windrows during 19 weeks. Typical monitoring parameters and gaseous emissions (CO2, CO, CH4, N2O and H2S) were evaluated during the process as well as the agronomical quality of the end-products. Biochar accelerated organic matter degradation and ammonium formation during the thermophilic phase and enhanced nitrification during the maturation phase. Our results suggest that biochar, as composting additive, improved the physical properties of the mixture by preventing the formation of clumps larger than 70 mm. It favoured microbiological activity without a relevant impact on N losses and gaseous emissions. It was estimated that biochar addition at 3% could reduce the composting time by 20%.

Nanobiocomposites of carrageenan, zein, and mica of interest in food packaging and coating applications.

The present study presents the development and characterization of biocomposites of a red-algae-derived carrageenan, mica, and their blends with zein prolamine obtained by solvent casting. The morphology of the blends was characterized by scanning and transmission electron microscopy (SEM and TEM), optical microscopy, and atomic force microscopy (AFM). Mechanical behavior, water barrier, water uptake, and UV-vis protection of the cast films were also investigated. The results indicated that the addition of 10 wt % glycerol to the blends resulted in a better dispersion of the additive and, for that reason, a better improvement for the studied properties. The composites were seen colored but transparent and exhibited the ability to block the UV-vis radiation because of the characteristic absorbing properties of the filler. Nevertheless, the main conclusion from the work is that the nanocomposites were seen to act as a reinforcing plasticizer and also led to significantly reduced water permeability and uptake. The clay was found to be more efficient in the latter aspect than the zein prolamine as an additive. As a result, these novel carragenan-based biocomposites can have significant potential to develop packaging films and coatings for shelf-life extension of food products.

Biochar increases soil N2O emissions produced by nitrification-mediated pathways

In spite of the numerous studies reporting a decrease in soil nitrous oxide (N2O) emissions after biochar amendment, there is still a lack of understanding of the processes involved. Hence the subject remains controversial, with a number of studies showing no changes or even an increase in N2O emissions after biochar soil application. Unraveling the exact causes of these changes, and in which circumstances biochar decreases or increases emissions, is vital to developing and applying successful mitigation strategies. With this objective, we studied two soils (Haplic Phaeozem (HP) and Haplic Calcisol (HC)), which showed opposed responses to biochar amendment. Under the same experimental conditions, the addition of biochar to soil HP decreased N2O emissions by 76%; whereas it increased emissions by 54% in soil HC. We combined microcosm experiments adding different nitrogen fertilizers, stable isotope techniques and the use of a nitrification inhibitor (dicyciandiamide) with the aim of improving our understanding of the mechanisms involved in the formation of N2O in these two soils. Evidence suggests that denitrification is the main pathway leading to N2O emissions in soil HP, and ammonia oxidation and nitrifier-denitrification being the major processes generating N2O in soil HC. Biochar systematically stimulated nitrification in soil HC, which was probably the cause of the increased N2O emissions. Here we demonstrate that the effectiveness of using biochar for reducing N2O emissions from a particular soil is linked to its dominant N2O formation pathway.

Morphology and Water Barrier Properties of Nanobiocomposites of κ/ι-Hybrid Carrageenan and Cellulose Nanowhiskers

The current study presents the development and characterization of novel carrageenan nanobiocomposites showing enhanced water barrier due to incorporation of cellulose nanowhiskers (CNW). CNW, prepared by acid hydrolysis of highly purified α cellulose microfibers, were seen to have a length of around 25-50 nm and a cross section of ca. 5 nm when dispersed in the matrix. The nanobiocomposites were prepared by incorporating 1, 3, and 5 wt % of the CNW into a carrageenan matrix using a solution casting method. Morphological data (TEM and optical microscopy) of the nanocomposites containing CNW were compared with the morphology of the corresponding biocomposites containing the original cellulose microfibers and the differences discussed. Thermal stability by TGA, water vapor permeability, and percent water uptake were also determined. The main conclusion arising from the analysis of the results is that the nanobiocomposites containing 3 wt % of CNW exhibited the lowest reduction in water vapor permeability, that is, ca. 71%, and that this reduction was largely attributed to a filler-induced water solubility reduction. This fully biobased nanoreinforced carrageenan can open new opportunities for the application of this biopolymer in food-packaging and -coating applications.

Compost vs biochar amendment: a two-year field study evaluating soil C build-up and N dynamics in an organically managed olive crop

Background and aimsDespite the high interest in biochar as soil amendment, the number of field studies is still limited, being experiments with perennial crops in arid lands particularly lacking. This study evaluated the application of compost and biochar in a drip-irrigated organic olive crop in a calcareous soil in South-East Spain.MethodsDuring two consecutive years, changes in soil total organic C (TOC), dissolved organic C (DOC) and water soluble N (WSN), mineral N (NH4+ and NO3−), N2O emissions, denitrifying enzyme activity (DEA) and number of amoA gen copies were monitored.ResultsBiochar increased TOC compared to the rest of treatments, whereas DOC and WSN significantly increased in plots amended with compost and the compost-biochar mixture. DEA, amoA-encoding genes and N2O emissions were highest with the compost-biochar mixture, but results were not always significant.ConclusionsOur results show that, in these N-limited and deficit irrigated semi-arid agro-ecosystems, compost amendment has an impact on soil microbiological activity with a link to N availability. Biochar applied alone does not alter the N dynamics, but markedly builds-up soil C. In both cases only during the first year these effects were statistically significant. When applied in combination a synergistic effect was observed and the highest values of DEA, amoA gene copies and N2O emissions were detected.