Studies on the anaerobic decomposition of plant materials: Comparison of the course of decomposition of rice straw under anaerobic, aerobic and partially aerobic conditions

Biomethanation of Rice Straw: A Sustainable Perspective for the Valorisation of a Field Residue in the Energy Sector

Rice straw represents a field waste. Indeed, only 20% of the rice straw produced is used in the pulp and paper industry. The larger amount of this field residue is burned or left in the field, which has very important environmental consequences. Recently, analogous to a barrel of oil, a metric approach to rice straw, the rice straw barrel, was introduced in order to assign economic value to this waste. In this paper, potential annual biomethane production from anaerobic digestion is evaluated, resulting in a range of biomethane created for each rice straw barrel depending on volatile solid (VS) content as a percentage of total solid (TS) content and on biomethane yield: 23.36 m3 (VS=73.8%TS, 92 L kgVS−1), 26.61 m3 (VS=84.08%TS, 186 L kgVS−1), 29.27 m3 (VS=95.26%TS, 280 L kgVS−1). The new concept of the rice straw barrel is improved based on a new indicator for sustainability, the Thermodynamic Human Development Index (THDI), which was introduced within the last three years. The improvement in sustainability by using rice straw barrels for different countries is analysed based on the THDI.

Effects of a Partially Perforated Flooring System on Ammonia Emissions in Broiler Housing-Conflict of Objectives between Animal Welfare and Environment?

Simple Summary

Previous studies have shown positive effects of a partially perforated flooring system on animal welfare in broiler housing. Towards the end of the fattening periods, the present study showed a higher ammonia emission rate (NH₃ ER) for a partially perforated flooring system compared with a littered control barn. Nevertheless, the measured NH₃ concentrations were below 20 ppm, except during a mechanical litter treatment in the winter fattening period. Furthermore, the system offers the possibility of applying practical solutions that were not feasible before. By using underfloor air extraction, manure belts, or acidification systems underneath the elevated perforated area, NH₃ concentrations and the resulting NH₃ ER could be reduced. Thus, with some optimization, the partially perforated flooring system could be used to contribute to an increase in animal welfare and environmental protection at the same time.

Abstract

A partially (50%) perforated flooring system showed positive effects on health- and behavior-based welfare indicators without affecting production performance. Ammonia (NH₃) is the most common air pollutant in poultry production, with effects on animal welfare and the environment. The objectives of animal welfare and environmental protection are often incompatible. Therefore, this study addresses the question of how a partially perforated flooring system affects NH₃ emissions. According to German regulations, three fattening periods were carried out with 500 Ross 308 broilers per barn (final stocking density: 39 kg m⁻²). The experimental barn was equipped with an elevated perforated area in the supply section, accessible by perforated ramps. The remaining area in the experimental barn and the control barn were equipped with wood shavings (600 g m⁻²). Besides the different floor types, management was identical. Air temperature (Temp), relative air humidity (RH), NH₃ concentration, and ventilation rate (VR) were measured continuously. Furthermore, dry matter (DM) content, pH, and litter quality were assessed. Towards the end of the fattening periods, the NH₃ emission rate (ER) of the partially perforated flooring system was higher compared with that of the littered control barn (all p < 0.001). This effect is mainly caused by the higher NH₃ concentrations, which are promoted by the lack of compaction underneath the elevated perforated area and the increase in pH value under aerobic conditions. Nevertheless, the partially perforated flooring system offers different approaches for NH₃ reduction that were previously not feasible, potentially contributing equally to animal welfare and environmental protection.

Causal mechanisms of soil organic matter decomposition: deconstructing salinity and flooding impacts in coastal wetlands

Coastal wetlands significantly contribute to global carbon storage potential. Sea-level rise and other climate-change-induced disturbances threaten coastal wetland sustainability and carbon storage capacity. It is critical that we understand the mechanisms controlling wetland carbon loss so that we can predict and manage these resources in anticipation of climate change. However, our current understanding of the mechanisms that control soil organic matter decomposition, in particular the impacts of elevated salinity, are limited, and literature reports are contradictory. In an attempt to improve our understanding of these complex processes, we measured root and rhizome decomposition and developed a causal model to identify and quantify the mechanisms that influence soil organic matter decomposition in coastal wetlands that are impacted by sea-level rise. We identified three causal pathways: (1) a direct pathway representing the effects of flooding on soil moisture, (2) a direct pathway representing the effects of salinity on decomposer microbial communities and soil biogeochemistry, and (3) an indirect pathway representing the effects of salinity on litter quality through changes in plant community composition over time. We used this model to test the effects of alternate scenarios on the response of tidal freshwater forested wetlands and oligohaline marshes to short- and long-term climate-induced disturbances of flooding and salinity. In tidal freshwater forested wetlands, the model predicted less decomposition in response to drought, hurricane salinity pulsing, and long-term sea-level rise. In contrast, in the oligohaline marsh, the model predicted no change in response to drought and sea-level rise, and increased decomposition following a hurricane salinity pulse. Our results show that it is critical to consider the temporal scale of disturbance and the magnitude of exposure when assessing the effects of salinity intrusion on carbon mineralization in coastal wetlands. Here, we identify three causal mechanisms that can reconcile disparities between long-term and short-term salinity impacts on organic matter decomposition.