Review of the rice production cycle: By-products and the main applications focusing on rice husk combustion and ash recycling

Abstract

One of the consequences of industrial food production activities is the generation of high volumes of waste, whose disposal can be problematic, since it occupies large spaces, and when poorly managed can pose environmental and health risks for the population. The rice industry is an important activity and generates large quantities of waste. The main solid wastes generated in the rice production cycle include straw, husk, ash, bran and broken rice. As such, the aim of this article is to present a review of this cycle, the waste generated and the identification of opportunities to use them. Owing to impacts that can be minimised with the application of rice husk ash as a by-product, this work is focused on the recycling of the main wastes. In order to achieve that, we performed theoretical research about the rice production cycle and its wastes. The findings point to the existence of an environmentally suitable use for all wastes from the rice production cycle. As rice, bran and broken rice have their main use in the food industry, the other wastes are highly studied in order to find solutions instead of landfilling. Straw can be used for burning or animal feeding. The husk can be used for poultry farming, composting or burning. In the case of burning, it has been used as biomass to power reactors to generate thermal or electrical energy. This process generates rice husk ash, which shows potential to be used as a by-product in many different applications, but not yet consolidated.

Comparative study using different external sources of aluminum on the zeolites synthesis from rice husk ash

“…Rice husk is an abundant waste material derived from agricultural production and has been used with great efficiency as an energy source through burning. It is used as a fuel in rice processing because it is a renewable energy source with a reasonable energy content of 12-18 MJ kg −1 and has a high transport cost due to low packaging [4,32].…”

“…This byproduct is produced worldwide and causes an environmental problem such as air and water pollution [1]. On the other hand, the chemical analysis reveals that RHA contains 90%-99% of silica, which can be a cheap source to be used in several industrial sectors [2][3][4]. Several researchers have utilized silica obtained from RHA as a raw material for production in solar grade silicon (Si-GS) [5], silicon carbide (SiC) [6], silicon nitride ceramics (Si 3 N 4 ) [7] and mullite (a fibrous alumina silicate mineral of low thermal expansion, formed within porcelain bodies during firing and in industry by calcining) [8][9][10].…”

Replacement of Commercial Silica by Rice Husk Ash in Epoxy Composites: A Comparative Analysis

“…The high silica content of RHA makes it a potentially interesting admixture with several industrial applications, as in the production of glass, refractory materials, pozzolanic material used in construction, silicon carbide, silicates, and pure silica. In addition, RHA may be used as adsorbent and reinforcing agent or filler in polymer composites [5][6][7] . Different applications require different processing and purification operations, such as grain size seggregation 8 , milling 9 , and acid leaching 10 .…”

Degrading Pesticides with Waste Product: Imidazole-Functionalized Rice Husk Catalyst for Organophosphate Detoxification

“…5 Despite these facts, research and use of cellulosic residues such as raw RH in the chemical industry is still a relatively unexplored field, thus the main destination of these materials is to burn as biomass or use as fertilizer. 1 The RH waste awareness is potentiated by some facts: rice is among the major crops worldwide, which is also one that most applies agrochemicals. 6,7 Specifically concerning Brazil's scenario, while it occupies fourth place in worldwide agricultural production, Brazil is one of the largest consumers of agrochemicals.…”

“…1 Notwithstanding, while rice feeds more than half of the human population, about 0.22 kg of RH is produced for each 1 kg of rice cropped, i.e., an estimated production of 164 million tons of RH only in 2013, according to data of FAOSTAT. 2,3 Furthermore, RH leads as the most underused cellulosic source in contrast to wood, textile fibers and papers.…”