Quarry Southern Africa May 2017 - Page 27

BENEFICIATION Feed material for C&D waste recycling. Development Planning) have C&D waste as one of their key focus areas. “At national level, the Department of Environmental Affairs has also been considering C&D waste and I know there’s a move internally to develop a project specifically focusing on this area,” she adds, “and we are hoping to be a part of developing the terms of reference for that project.” According to Nicolan Govender, regional manager for sub-Saharan Africa at wet processing equipment company CDE, there’s huge cost involved in disposing of C&D waste, including transport and disposal costs. What C&D waste recycling does is remove the cost associated with disposal of C&D waste by transforming it into an income-generating, high quality sellable aggregate. Wet processing C&D waste can generally be divided into two types: inert materials such as sand, bricks and concrete, and non-inert materials such as plastic, glass, paper, wood, vegetation and other organic materials (Ulubeyli et al., 2017). Prior to processing, the waste is sorted to remove as much undesirable material as possible. With dry processing, which is the method historically used in South Africa, the material is then processed using either static or mobile crushing and screening equipment Recycled concrete material. before being reused in one of a variety of applications. For the smaller companies using mobile equipment, this is often done at the demolition site. However, for the contractor the cost of doing this is high compared to the profits they make. In this sort of arrangement, it’s usually the big construction company reaping the benefits because they are getting their material rehandled, recycled and reused on site, while the contractor benefits less because of the low margins. Nicolan Govender, regional manager for sub-Saharan Africa for global wet processing company CDE, says that the next step for companies looking to increase their profits is to add a wet process to their dry crushing and screening operations to immediately achieve a higher value product. “If you think about it, dry crushing and screening simply reduces the material used in constructing a building – all the organics and contaminants are still in there. With wet processing, you float off all the lightweight organics and contaminants, and then use a wet screening process to size and clean the sand,” he explains. CDE prides itself on being the market leader in wet processing C&D waste recycling, specifically of sand and aggregates. Govender explains that a CDE processing plant will take in your typical C&D waste – such as concrete, bricks, blocks, some organics such as grass, Guidelines Guidelines are being developed to help C&D waste recyclers work within the parameters of legislation and best practice as dictated by various professional bodies within the construction industry. These laws and practices include: • Applicability of legislation and legal requirements • Best practice sourcing and separation at source • Best practice crushing and screening • Best practice stockpiling/blending of crushed materials • Material specifications for use in roads • Material specifications for use as concrete aggregates • Best practice design, construction and quality control Source: Aspasa plastics and wood – as feed material and separate the sand from the stone to produce a high quality washed, manufactured sand that can be sold back to the construction industry. “The CDE system comprises AggMax scrubbers to clean up the material, an EvoWash washing plant to wash the sand, an AquaCycle thickener to recycle up to 90% of the water used in the washing plant and, in some cases, a filter press, which creates a solid waste cake of fine material out of the sludge from the Aquacycle,” says Govender. A flagship project in this area for CDE is the Germany-based CANDY Project (which stands for ‘CompAct, highly mobile, Next generation, CD&E waste recoverY system), backed by the European Union’s Eco-Innovation Fund, which aims to enhance the infrastructure for the recycling of C&D waste in Europe. The project’s technical objectives include enhancing the mobility and reducing the plant footprint of the waste recycling plant, as well as increasing the quality of the washed recycled sand and aggregate products. The project also aims to offer new sludge management technology with a focus on maximising the recovery of process water for recirculation to the washing plant. There’s huge cost involved in dumping C&D waste – including transport costs, dumping costs at the landfill, and so on. According to Govender, many CDE customers, including the CANDY Project, are in waste removal. “One of the advantages of a CDE plant is that we take the mixture of waste that would normally be dumped at a landfill and turn it into a way to generate revenue rather than an expense. Ordinarily, our customers in waste removal would have a contract from a major construction company to take the waste from demolished buildings offsite and dump it,” he says. “The companies don’t really care where the waste is going, they just nominate someone to come in and take care of it. What we’re saying to our customers is rather than paying to QUARRY SA | MAY 2017 _ 25