MechChem Africa March-April 2025

AES: Powerful support for carbon footprint reduction Although many manufacturing and industrial companies have stated objectives to reduce use of fossil fuels, there are not yet any silver bullets in the green fuel space, says Dennis Williams, Commercial Director at steam and boiler operations and maintenance service provider, Associated Energy Services (AES). S upply and logistics constraints, high costs and technological limitations are just some of the challenges encountered by AES as they assist per gigajoule, which is about four times the cost of coal.

Using biomass Williams says bagasse, derived from sugar cane residues, was probably the earliest biomass fuel used in South Africa: “The busi ness models for this have changed substan tially over the years. Bagasse was regarded as a problem. This view has been turned on its head, to the point where local sugar mills maximise its use as energy feedstock in their boilers for steam and power generation.” In the timber industry, the focus is on maximising the useful yield from timber. Each log is scanned to determine the sizes, widths and thicknesses which can be cut; as well as the potential waste. White wood chips are often sold for board manufacture, typically leaving contaminated wood chips, saw fines and bark for energy generation. Other biomass options are macadamia shells, sunflower husks and residue from maize harvesting. Seasonality and crop yields impact supply, however, while rural locations increase transport costs and ve hicle emissions. The potentially alkaline chemical com

position of agricultural waste can damage boilers and heat transfer surfaces. The ash characteristics are also problematic, Williams notes. When researching the use of sunflower husk for a client, AES found it challenging to find a workable and sustainable solution: “For years, there was a glut of sunflower husks in the market. Then, suddenly, sun flower seed pricing turned and it became more cost-effective for local manufactur ers to import sunflower oil than to process sunflower seeds themselves. This put the viability of the project into question,” Williams recalls. Wind and solar energy for steam boilers The greatest challenge with using wind and solar power generation solutions in electrode boilers are the transmission constraints of the power grid, with renew able energy companies unable to export electricity to the national grid without

an increasing number of clients to inves tigate the use of more environmentally sustainable, lower carbon fuel alternatives – thereby obviating the requirement to pay carbon taxes both locally and abroad. “When a global business decides to reduce its carbon footprint – or even go carbon neutral – this decision seems to be applied across all marketplaces, irrespective of the local economic pressures and techni cal challenges.” One AES client is already running out of time to meet the ambitious decarbonisation target of its global parent company: “We have reviewed all options – from electricity to solid fuels, liquid fuels, different gases, biomass and agricultural residues – and shown the capex, opex and supply dynam ics on multiple occasions. We have also considered the amount of space needed, and the consequences of each fuel choice from an emissions and carbon tax perspec tive. In addition, we have looked at how much the steam will cost, the amount of ash that would be generated, and how to deal with that.” Williams’s key message is that carbon taxes are here to stay and that companies and consumers will not be able to absorb the costs of using fossil fuels indefinitely. Companies must be educated about differ ent options that suit their specific needs. For Williams, gas is best regarded as an interim step on the decarbonisation journey: “Not only is supply an issue in terms of gas, but it remains a fossil fuel with a carbon footprint. Companies will still pay substan tial carbon tax and find themselves only part of the way to a zero carbon target. There is naturally also a cost associated with making this interim switch, so it is a less than ideal option in most cases.” Apart from the predicted local shortages of natural gas, converting and transporting this fuel as liquefied natural gas (LNG) is not environmentally friendly and is expensive, with recent price indications at US$18-$20

In the timber industry, white wood chips are often sold for board manufacture, typically leaving contaminated wood chips, saw fines and bark for use for energy generation.

16 ¦ MechChem Africa • March-April 2025