Search

In recent years, agro-industrial residues are focusing attention worldwide as a new source of pozzolans; in Brazil one of the wastes generated from agro-industrial activities comes from elephant grass that is cultivated as biomass for energy cogeneration. The goal of this paper is to analyze the influence of elephant grass, once activated at 700 °C for 1 h in electric furnace, on the evolution of the hydration reaction as well as physical and mechanical properties in blended cement elaborated with 20% of elephant grass ash. For the present study, different instrumental techniques of characterization and methodologies (XRF, XRD, TG/DTG, mercury porosimetry, isothermal calorimetry and mechanical strength) were used. The results obtained in the present work show, that due to its high pozzolanic activity, the elephant grass ash activated at 700 °C can be used as an alternative pozzolan in the blended cement manufacture. Additions of 20% of ash confirm the formation of CSH gels and hexagonal C 4 AH 13 as main products from hydration as well as pozzolanic reaction. The 20% ash blended cement showed lower heat evolution than OPC and similar to the 20% silica fume blended cement, a 12% of reduction of compressive strength and an important reduction of pore sizes below 50 nm. [ABSTRACT FROM AUTHOR]

Greenhouse gas emissions related to food production in selected countries around the world in 2000, 2007, and 2014 were analyzed in this paper. In recent decades, many studies have suggested that greenhouse gas emissions mostly caused by agricultural production should be reduced. However, a low-carbon agricultural sector often involves a reduction in inputs, which may result in smaller production volumes. Nevertheless, the overarching goal should be to maintain food production at a sufficient level to meet the population's food requirements. Food production is particularly important in the context of the forecasted growth of the world population. In this situation, greenhouse gas emissions per product unit should be regarded as a key indicator that reflects the environmental sustainability level of production processes. Defined as such, environmental sustainability was examined across the entire food production system—referred to as agribusiness. This study calculated the emissions of major greenhouse gases related to food production and compared them to the GDP of agribusiness. The average ratio of the agribusiness carbon footprint to GDP in countries examined was nearly 2 kg of CO 2 equivalent/USD in 2000. This value kept decreasing during the study period, reaching 1.21 in 2014. A decrease in the ratio was recorded despite an increase in agribusiness greenhouse gas emissions, which validated the research hypothesis that an increase in greenhouse gas emissions from agribusiness does not necessarily reflect a decline in the environmental performance of agribusiness production. This is especially true for China and Brazil, whose greenhouse gas emissions related to food production increased considerably in the years examined in this study along with a clear decline in emission levels per unit of agribusiness GDP. This study is innovative, because the literature does not provide any similar calculations for the food production subsystem, especially regarding emission levels per production unit. This approach required the authors to integrate the calculation methods used in agribusiness production with those applicable to agribusiness greenhouse gas emissions. Thus, this study relied on consistent methods developed by the authors to calculate these values. The research adds to existing literature by calculating the carbon footprint for the entire food production system, and it argues that better environmental performance of agribusiness production can be achieved despite higher greenhouse gas emissions. [ABSTRACT FROM AUTHOR]