Agricultural waste

The current status and future of solid waste recycled building bricks

Solid waste (SW) has become a problem hindering the economic and social development. Achieving the full green cycle from raw material to production of recycled building bricks (RBB) using SW is the focus of future research. In this paper, the research results of RBB manufacturing using SW in recent years are reviewed. According to the consolidation principle of RBB, the effects of different types of SW on the physicochemical properties and microstructure of RBB are summarized based on the recycled unsintered brick (RUSB) and recycled sintered brick (RSB). By comparing and evaluating the two consolidation methods, it is proposed that RSB has good practicality due to its higher SW utilization rate, higher strength, and faster consolidation speed. Furthermore, the difference between MWS and conventional sintering (CS) is analyzed, and the research on the application of MWS in SW-RBB manufacturing in recent years is reviewed in detail. It is pointed out that microwave sintering (MWS) technology can solve many drawbacks in traditional sintering technology and has great prospects in manufacturing SW-RBB due to the low energy consumption, low pollution, and high efficiency. Finally, the shortcomings and possible challenges in the current research on manufacturing SW-RBB using MWS technology are discussed, which provides guidance for the future development of SW-RBB manufacturing.

Study on the Quality of Mixed Silage of Rapeseed with Alfalfa or Myriophyllum

The objective of this study was to improve the comprehensive rate of utilization of rapeseed (Brassica napus subsp. napus L.), Myriophyllum (Myriophyllum spicatum L.) spicatum and alfalfa (Medicago sativa L.), reduce resource waste and environmental pollution. In this experiment, the effects of different proportions of the mixed silage of rapeseed and alfalfa or M. spicatum on the fermentation and nutritional quality were analyzed and further improved the quality of mixed silage using molasses and urea. Rapeseed was separately silaged with alfalfa and M. spicatum based on the ratios of 3:7, 5:5 and 7:3. After 60 days of mixed silage, the fermentation index and nutrient contents were measured to explore the appropriate ratio of mixed silage. The mixing ratio of rapeseed and alfalfa was better at 3:7: The contents of NH₃-N/TN (4.61%), lactic acid (96.46 g·kg^-1 dry matter [DM]) were significantly higher (p < 0.05). The crude protein content (118.20 g·kg^-1 DM) was the highest (p < 0.05), while the pH (4.56) was the lowest when the mixing ratio of rapeseed and M. spicatum was 7:3. Considering the fermentation and nutrition quality, it is suggested that rapeseed and alfalfa should be mixed as silage at a ratio of 3:7 with 3% molasses and 0.3% urea, and rapeseed and M. spicatum should be mixed as silage at a ratio of 7:3 with 3% molasses.

Eco-friendly geopolymer prepared from solid wastes: A critical review

Solid wastes are generated from human activities which could cause damage to the ecological environment and human beings. In recent years, there has been extensive research on solid wastes utilized as precursors, aggregates, fibers, etc. to prepare the geopolymers, which has invariably been a research hotspot. This review classifies the solid wastes utilized for geopolymers into three main categories: industrial waste, agricultural waste, and municipal waste. Accordingly, we systematically dissert solid wastes-based geopolymer from the perspectives of structure, properties, and application. The chemical composition, morphology, particle size, thermal conductivity, and other characteristics of solid wastes can trigger changes in the specific properties of geopolymers. On this account, solid wastes-based geopolymers have great potential in the domain of concrete, fireproof materials, impermeable materials, catalysts, adsorbents, and energy storage materials, etc. More importantly, geopolymers have obvious advantages in immobilizing heavy metals in solid wastes. Therefore, it can demonstrate geopolymer is a sustainable and environmentally friendly "green material". However, it still confronts the challenges of solid wastes utilized in geopolymer (technology, economy, administration). It requires the government, enterprises, and the public to work together for co-governance to accomplish industrialization and commercialization of solid wastes-based geopolymer.

Food waste composting - Is it really so simple as stated in scientific literature? - A case study

Food waste has recently gained much worldwide interest due to its influence on the environment, economy and society. Gathering and recycling of food waste is the essential issue in the waste management and the interest in processing food waste arises mainly out of influence of the processes of food putrefaction on the environment. Composting of food waste encounters a number of technical challenges, arising weak physical structure of food waste with weak porosity, high content of water, low carbon-to-nitrogen relation and fast hydrolysis and accumulation of organic acids during composting. Therefore, the aim of this study was to investigate the challenges facing installations intended for food waste composting, with the purpose to their optimization with use of appropriate additives. Physico-chemical, biochemical characteristics and phytotoxicity of the produced compost has been measured. Two additives (20% biochar and 20% sawdust) were chosen from experimental variants I-XII containing different additives (biochar, Devonian sand, sawdust) in diverse concentration. The use of selected additives seems to slightly increase potential of hydrogen value and carbon-to-nitrogen ratio, while decreasing electrical conductivity in comparison with control sample. The results obtained also show that the addition of biochar leads to an increase dehydrogenase, phosphatase and arylsulphatase activities and addition of sawdust has a positive effect on beta-D-glucosidase, protease, phosphatase and arylsulphatase activities. The phytotoxicity test shows that the compost made of food waste (control sample) and with addition of biochar is toxic to plants. By contrast, the addition of sawdust shows that the compost was not phytotoxic. In conclusion, the addition of additives does not provide unambiguous results in terms of the quality of the final product in all monitored parameters. Therefore, we can state that food waste was reduced and hygienized, and that the final product does not meet conditions for mature compost.