Fuelling the future

In January 1999, the world witnessed the end of a century of cheap oil. It then cost less than $20 per barrel. Few predicted it would reach the $100+ levels of today. Some are predicting $500 oil by 2020. This would be devastating for Mauritius, not only for tourism but for most of our industries and our quality of life. Well before this level is reached, it will be cost effective to convert coal into oil, as South Africa has done for decades, causing coal prices to increase too. Is it possible to avoid catastrophe and reduce our dependence on fossil fuels?

Mauritius: Island of Dreamers (MID)

In contrast to the propaganda trumpeting our green credentials, in reality, our dependence on fossil fuels continues its inexorable rise. Offering generous feed-in-tariffs for the rich to install expensive photovoltaic panels is effectively a tax on the poor. Why not simply wait until they become affordable? Rodrigues already has more wind turbines than its network can cope with and the main island is not so far behind. Extracting significant geothermal energy from extinct volcanoes is unlikely; the geological hotspot moved to Reunion long ago. Despite years of talk, we are still not utilising cold, deep ocean water for air conditioning let alone electricity production. Back to the drawing board?

Simple substitutes

Fossil fuels, which are essentially stored ancient sunlight, take three forms: solid, liquid and gas; predominantly coal, oil and methane. Mauritius has substitutes for all three. Instead of coal, when the settlers arrived they burned wood from our once ubiquitous forests. Now we burn what replaced them – waste from the sugar industry – bagasse. During the second world war, we used ethanol in our cars but we have been incomprehensibly reticent to recommence. Methane produced in the St Martin waste water treatment plant and at the Mare Chicose landfill is now used to make electricity. However, these substitutes have little impact on our consumption of fossil fuels. Can we do better?

Efficient and flexible electricity

When fuels burn they release heat as they oxidise into carbon dioxide and water vapour. When internally combusted in car engines, expansion of the hot gases drives pistons, while in aircraft engines the expansion drives a turbine. In a power station, this motive power is converted into electricity by a generator – effectively an electric motor in reverse. In a solid fuel power station, however, the expansion of the gases is wasted and the heat is used to boil water into pressurised steam whose expansion in turn drives a turbine. Because of this intermediate step, steam-based systems are less efficient and less flexible than internal combustion engines, which explains why they are no longer used in ships and trains. Combined-cycle engines that harness gas expansion and residual heat are more efficient still, albeit at the expense of some flexibility. Fuel cells that produce electricity directly from the transfer of electrons during the oxidation reaction have the potential to be even more efficient, but they are still in development.

Mauritius has the natural resources to generate an abundance of electricity from wind and solar power, however, these sources are intrinsically variable. Hence, we must either store electricity, which is currently too expensive, or balance variable sources with very flexible ones. Coal/bagasse power stations are simply not up to the task, and oil and methane are destined to become prohibitively expensive. We could ferment all our sugar into ethanol, but a lot of energy is wasted in distillation. Is there an alternative?

Grass is greener

While sugar-cane is very efficient in utilising sunlight, other plants are even better. Energy grasses are being hybridised to maximise their photosynthetic yield and can produce four times more than sugar-cane. By utilising the same process harnessed at St Martin and Mare Chicose (anaerobic digestion), freshly cut green grass can be biologically converted into methane to produce electricity. Moreover, the residue from the conversion process is an ideal amendment to help restore the fertility of our soils that have been exhausted by centuries of non-stop mono-cropping. Methane can power the most flexible and efficient engines and while it can be stored in tanks, the best approach is to leave the grass growing in the fields and harvest it on an as needed basis. Unlike sugar-cane, the crop can be cut throughout the year.

There are currently over 10,000 hectares of abandoned sugar-cane fields which could be utilised to generate income for their owners and electricity for the nation. Modular power plants can be placed throughout the country to minimise the transport of the grass and help balance the grid. Is there a better way to democratise electricity production? As the other small planters see their colleagues realising a better return on investment, they will also convert their cane fields to energy grasses. In a short time, Mauritius can have significant flexible capacity, permitting the integration of a high proportion of wind and solar power. We can become a leader in renewable energy, setting an example to the world. What a story to tell at Rio+20 in June?

Freedom from fossils

Fossils are not only found in the ground. With a few world-class exceptions, Mauritius has been lamentable at preserving endangered species. However, reserves protecting fossilised thinking are everywhere: within the government, CEB, the university, sugar estates and quasi-religious cults. We can set ourselves free from fossil fuels but not before the dinosaurs become extinct.

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One comment

  1. Dr Mu

    Thanks to Guillaume Maurel for pointing out that our soils are so depleted that special steps need to be taken to restore them. The first step is to correct the chemistry, this improves the physical properties of the soil which in turn allows the organic components to re-establish and thrive. Once a natural organic balance has been achieved, nutrients lost when the grass is harvested can be replenished using the distillate from the anaerobic digestion process. One further problem is that the soil is contaminated with heavy metals. These will be slowly extracted by the grass but would need to be removed from the subsequent distillate. The same problem arises when using products from waste water processing as fertiliser. A number of solutions are available including aquatic plants, aglae, acid from fermented pineapple waste, and nanomaterials.

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