Coal to concrete: Converting waste to resource
Once a coal mine’s reserves are exhausted, it is left abandoned, along with all the waste generated by the mining process. This waste, if left unprocessed, can harm the environment and nearby communities for decades together. On the other hand, increasing urbanisation is catapulting the demand for construction material, the production of which is very carbon-intensive.
Dr Binish Desai, CEO, Eco Ecletic Tech and better known as the Recycle Man of India, has found a way to solve both these problems by making coal waste a resource for manufacturing a substitute of concrete, called Gobcrete.
In this interview, he speaks about how coal waste is processed, the characteristics of the product and other construction-related innovations.
How is waste from coal mining currently processed? How does your approach differ?
Bituminous coal mining generates waste known as Garbage of Bituminous (GOB), which contains iron, manganese and aluminium and causes acid drainage, sediment release and release of fine coal particles that can harm waterways. Additionally, GOB piles emit greenhouse gases, including carbon dioxide and methane, as well as toxic substances such as carbon monoxide and mercury. Coal dump sites produce 1,200-8,200 kilograms CO2/m2 per year.
Conventionally, shale and sludge is washed off from this waste, and only low-quality coal is recovered. Our process is different; for us, shale and sludge are precious resources, and low-quality coal is a byproduct. We reuse every component of GOB.
The process actually captures carbon dioxide from the atmosphere and stores it in the product. By preventing coal waste from harming the environment as well as trapping atmospheric carbon dioxide, the process is carbon-positive. – Dr Binish Desai
What processes do you put GOB through?
Washing: The material is thoroughly washed and churned. The process divides it into sludge, large shale, tiny coal pieces and grey water. The grey water is filtered and reused back into this process.
Sieving: The sludge goes through an additional process where it is separated into medium-sized particles (which are directly used as a replacement for sand in Gobcrete), large particles and wet slurry.
Drying and crushing: All the particles, including sieved large particles mixed with large shale and wet slurry, are dried and crushed. The washed and separated tiny coal pieces are dried, crushed and given for charcoal manufacturing.
Eco Processing: All the ingredients extracted are mixed together along with our eco binder to create a mixture which after drying, becomes Eureka Gobcrete.
What does Eco Processing entail?
In the US, where Gobcrete was first prototyped, ARsoy, a by-product of the food-grade soy isolate production process is used in the development of Gobcrete. Similarly, in India, an agro-waste-base binder is used. The binder acts as an interface between slurry and shale.
The components of Gobcrete go through the physical change of hardening, as well as a patented biochemical process, during which it loses moisture. No external heat is involved, and the entire process is fuelled by solar power.
The process actually captures carbon dioxide from the atmosphere and stores it in the product. By preventing coal waste from harming the environment as well as trapping atmospheric carbon dioxide, the process is carbon-positive.
Tell us more about characteristics of Gobcrete itself.
It is a natural thermal insulant. A house built from Gobcrete is likely to remain cool indoors, even if outside temperatures rise.
Its water absorbance is the same as that of concrete; using it for construction can reduce costs by 40%, compared to conventional construction materials.
Through a life cycle analysis, we have found that the binding agents used have a life of 120 years, while the other raw materials (waste from coal mines) have been shown to last for centuries. Over the natural course of time, the properties of Gobcrete will remain constant.
Conventional concrete has various grades. Gobcrete offers the strength of M45 concrete while utilising raw materials in the ratio of M15 concrete.
At the end of its lifecycle, it can be recycled back into the same product, or broken down into the original three ingredients: shale, slurry powder and binder.
What are the potential applications of Gobcrete?
These include bricks and blocks, premix, precast products, industrial flooring, retaining walls, paving, sidewalks, driveways and parking lots, countertops and decorative panels. We are also exploring other applications like 3D-printed homes, which are the future of the construction industry.
While the raw materials will remain the same for each application, their ratios may differ.
What are your plans for this innovation?
A patent application has been filed with the US Patent and Trademark Office (USPTO) for this innovative prototype material and process. We are currently in the process of commercialising the material, and are looking for funding for further research and development, as well as investments to set up a large-scale manufacturing facility.
There are coal mines everywhere in the world and they all face the same issue. We believe our process and product has potential across the globe.
Tell us about your efforts to make movie-making sustainable.
We have collaborated with various big production houses to help reduce their carbon footprint, by advising them on how to make their sets, and the filming process, carbon-negative. When a movie set is broken down, valuable items may be auctioned off or reused in the next production, but Plaster of Paris – which constitutes the bulk of any set – tends to be dumped. We have helped productions recycle this, as well as plastic waste, packaging waste and other kinds of waste.
We also help them calculate their carbon emissions from various sources like flights to and from the location, diesel generators, prosthetics making etc, and reduce this as much as possible. Over the last two years, we have helped six movie sets be eco-friendly, with many more in the pipeline in the coming year.
Tell us about your flower waste-to-bricks project.
Flower waste from religious places usually enters water bodies. At the most, it is recycled into agarbattis.
We are setting up a small centre to collect flower waste from Ujjain’s Mahakaleshwar temple, and use it to make puja thalis, small decor products, eco-pilgrimage products and most importantly, bricks. Pilgrims can bring their flower waste to the centre, and take back a brick for constructing a new home, or donate it to the temple itself to build a community centre in the future. One day, maybe an entire temple can be constructed.
Features of Gobcrete
- Environment friendly and 100% recyclable
- Carbon-negative manufacturing process
- Strong and durable
- Reduces mortar consumption
- Energy-efficient
- Fire-retardant and pest-resistant
- Accurate dimensions and perfect surface for plastering
- Natural thermal insulation and suitable for all weathers
Properties of Gobcrete
- Compressive strength:
400-1,200 kg/cm2 - Grade strength: M40-M45
- Water Absorption: 10-15%
- Density: 450-800 kg/m3
