Background
The largest problem faced by any political party in power in South Africa is the decrease in sustainable permanent jobs and delivering of services such as refuge removal, clean water and sanitation and uninterrupted power supply. Without these basic services, there can be no economic growth and no improvement in the lives of the very poor and vulnerable. It is time to clean-up our streets and start building sustainable cities and communities were all has access to the economy and basic services as set out in our country’s hard-won constitution.
This document proposes a plan to do exactly that. The Waste Baseline report of 20`1(DEA, 2012) reported that approximately 91% of waste in South Africa was deposited on landfill sites. A mere 10% of landfill waste was recycled. A total of 59% of waste was classified as general waste of which 13% is organic waste. Approximately 35% of organic waste is recycled. General waste is estimated to grow by 2-3% per year. Only 6% of the 673 million ton of sewage sludge generated in 2012 was treated and only 19% was recycled back into the water system. About 30% of generated sewage was landfilled. On average we thus loose more than 50% of domestic water in the municipal treatment process.
Proposal
Different waste treatment technologies are compared in Table 1.
| Technology | Investment Cost (R/ton) | OPEX long term (R/ton) | Estimated revenue (R/ton) |
|---|---|---|---|
Table 1 – Comparison of waste treatment technologies
Landfill is the current practice, but this technology does not deliver any revenue. Anaerobic digestion (AD) seems profitable but has given mixed results when implement at different municipal sights in South Africa. One of the biggest drawbacks is the process’s sensitivity to the of feed composition and the fact that an additional waste stream is created in the form of the AD sludge that contain harmful bacteria. Pyrolysis and gasification is excellent for relatively fry feeds such as waste tyres and waste plastics.
Pyrolysis have been proven as a good technology to use for waste tyres and plastics, but suffer from high energy consumption for drying costs when wet waste streams are treated.
In this document we propose a new technology that can process both the primary sewage and the organic fraction of the municipal solid waste into revenue. The technology is called hydrothermal liquefaction (HTL) and can deliver not only clean sterilised water for domestic use, but also a variety of other products that can be utilised by the municipality for revenue creation. Table 2 show the products and revenue per hour that can be obtained from the organic fraction of municipal solids waste and primary sewage from Ekurhuleni municipality.
Product yields used in calculations are based on the work of the SARChI Research Chair in Biofuels at the North-West University (Prof Sanette Marx) and are based on real experimental data and not projections. Prices to calculated revenue is based on bulk market selling prices. The calculated revenue is based on the difference between input and output costs and does not include CAPEX and OPEX. A positive profitability at this level assures continuation of the development of a concept process design (CPD) which would give a better accuracy for estimating profitability.
| Item | Quantity |
|---|---|
| Item | Quantity |
|---|---|
Table 2 – Estimated products and profitability for Ekurhuleni municipality