The amount of global agricultural produce is ever-increasing with the rising human population, and so is the amount of agricultural waste produced. Much of the solid waste produced by the agriculture industry ends up in landfills or gets incinerated as people are unaware of what can be done with agro-waste. A seemingly unrelated industry, the modern construction sector, is on a mission to source building materials sustainably due to dwindling natural resources and rapid urbanization. Can we find an opportunity in this situation and attempt at creating an arrangement that is beneficial for both sectors? Can agricultural waste be used to serve the construction industry, systematically?
Why reuse agro-waste?
In the last 50 years, agricultural production has increased by 3 times. The human population is said to exceed 10 billion by 2050 and currently, the world produces about 24 million tons of food annually. Every step of the agricultural production, processing, and consumption creates huge quantities of solid wastes which vary from one crop to another depending on the purpose for which it is being cultivated. These wastes are mindlessly dumped in public spaces and water bodies or openly burnt resulting in air pollution, contamination of soil and water. Hence, for human health, animal health, and environmental well-being, it is necessary to find ways to repurpose agricultural waste.
Agro-waste as building materials
Solid crop waste in the form of husk, fibres, and leaves can be reused in many ways and one method is to use it in building construction. Research indicates that agricultural wastes such as rice husks, rice straw, peanut shells, and coconut shells can be used in partial replacement of sand in the manufacture of cement blocks adhering to the building standards with respect to strength and durability. The following is a list of a few easily manufacturable agro-based construction materials that have been developed from crops like rice, sugarcane, bamboo, coconut, palms, and varieties of timber:
- Rice Husk Ash (RHA)
- Sugarcane Bagasse Ash (SCBA)
- Bamboo Leaves Ash (BLA)
- Groundnut shell (GNS)
- Sawdust (SDA)
- Oil palm shell (OPS)
- Cork waste ash (CPA)
- Coconut shell (CNS)
Traditionally, coconut coir and rice husk are materials that have been used in buildings in mixture with earth, acting as a strong reinforcement to hold the clay and sand particles together. Fibrous materials aid in the tensile strength whereas binding materials aid in the compressive strength of a building. Even eggshells have been used as construction materials in the past. The idea of using naturally available materials as construction materials has existed from Neolithic times. The twentieth century saw the advancement of energy-intensive materials like steel and concrete and they have taken over the construction scene as mainstream building materials.
At present, there is a surge in awareness about the use of biomaterials for non-hazardous construction. Conventional construction materials such as cement and concrete require significant amounts of thermal and electrical energy, and this translates into higher costs. Therefore, a need arises to come up with building materials that are less energy-intensive and less expensive without compromising on the building quality. Apart from having less embodied energy, materials developed from agro-waste are also better suited environmentally because they exhibit higher thermal performance. This creates a closed-loop and bridges the gap between the agriculture and building construction sector.
How can agro-based materials be used?
A farm of any scale from the scale of a backyard or a rooftop to the scale of many hectares can convert agro-waste into building materials. Farmers can collect their bio waste, and either use it on-site for construction purposes if required or sell it to the growing industry of eco-friendly building materials. Further, these materials can be used in the composition of brick/masonry elements, green concrete, insulation materials for buildings, reinforcement materials for buildings, particleboards, and bio-based plastics. Biomaterials in general exhibit characteristics of strength and better binding properties in their natural state itself.
For example, if one is growing sugarcane to extract sugar or sugarcane juice, there is a significant amount of fibre that is generated as a by-product. The sugarcane by-product is called Bagasse, and it can be converted into a strong building material. Bagasse fiber is blended with water to remove any remaining sugar particles and is further developed into a pulp. This pulp is compressed under temperature and pressure to form a strong, sturdy, and fibrous material. Bagasse can be made into particle boards that can be used as partition walls or made into furniture.
Another example is GNS or Groundnut Shells which account for 20% of the dried peanut pod by weight and has a lot in common with wood since both are made up primarily of cellulose and lignin. Studies indicate that since peanut shells are weather-resistant, insect-proof, and resistant to fire, peanut farmers have a tough time trying to discard them. They generally end up in large mounds in landfills since nobody knows what to do with them. However, these properties are perfectly suited for building material and the fact that it is readily available as what it is makes it even easier to convert it into a product that can be used in the building industry. Groundnut Shell boards have become increasingly popular as a green building material in the last few years and farmers can make use of this to capitalize the waste that they find difficult to dispose of.
It can be the choice of the farmer to decide to what extent they can convert the waste into something useful. Either one can completely carry out the recycling process on their site in a different unit, or send the raw material to another agency specialized in developing biomaterials. One may use the material for the construction of farmhouses, storage spaces, or any building development that may be required on-site. If there is no plan of building any structure on-site, they can sell the material as a product for others who are wanting to use it and thereby generate additional income using the waste itself. What one can directly do with their agro-waste, depends completely on what are the requirements and capabilities in terms of time, money, and space availability.
Agro-materials are location-specific
The kind of agro-waste available in a given region will vary based on the crops that are cultivated in that particular region. For example, in South India, Rice Husk Ash (RHA) can be manufactured easily and in large amounts, considering the amount of rice that is consumed in the region. In coastal regions like Florida, Miami, and Kerala, coconut shells can be used to serve the building industry. China can make use of the large amounts of walnut shells that they produce. Using locally available materials for construction means there is less embodied energy involved and hence the usage of any of these materials will be more sensible in its native location.
Creating agro-based building materials is viewed as an ecologically viable option among the more developed countries, whereas in the developing countries it is seen from the perspective of economic gains. Particularly in developing countries where the amount of waste generated is higher, the awareness about possible risks and the potential benefits is low. Whichever perspective is chosen to look at this topic, the results occur in both ways. Environmentally, these materials lead to an overall reduction of greenhouse gas emissions and reduced usage of fossil fuels, and economically, it contributes significantly to the growth of new green markets and the creation of new jobs.
Food and shelter are the two basic needs of any human being, and these have developed over time to become the two biggest sectors in human society, namely the agriculture sector and the building construction sector. The development of agro-materials can bridge the gap that has arisen between these two industries to a certain extent and a circular system can be put into practice from the grassroots levels to global policy levels. Creatively intersecting these two industries will help to achieve economic, environmental, and social sustainability in the long run.