By: Michael Ryan
The solution to decarbonising our future energy demands does not lie with one individual technology. Rather, the solution lies in a portfolio of green technologies. The use of wind, solar and tidal, along with developments in hydrogen fuel cells and next gen batteries, will lessen our dependence on fossil fuels over time.
A crucial component of this green portfolio will be biomass, with this article focusing on plant based forms. There are challenges to be overcome. Land use is one. Where will we find room to grow these crops when our agricultural land use is already creaking at the seams? Crops such as willow, miscanthus and reed can provide a unique solution. They thrive in ‘badlands’, or areas deemed unsuitable for agricultural use. These crops also have bio regenerative properties. Areas experiencing a contamination of the water table have found the effects alleviated, and in some cases, reversed.
But what of the technical aspects of biomass? A detailed thermodynamic analysis of willow, for example, show it to have a higher calorific value to that of peat, but lower than that of coal. The particulates it releases during combustion contain less harmful NOX and SOX. But, far more foreign particles are present too. This can result in fouling and slagging in the boilers and tubes of modern powerstations. What does this mean in practical terms? Coal powerplants converted to biomass would need vast more quantities of fuel processed to produce the same amount of energy. This extra provision would put a massive strain on conveyors and loading systems.
What of peat powerplants? The powers that be recognise that peat conversion to biomass is a more workable method of large scale biomass power generation. The CAPEX costs of building a uniquely biomass powerstation would drive the cost per megawatt hour (MWh) of electricity of this form skywards. So, at present, the focus is on the conversion of existing plants. And, as it has a higher calorific value than peat, less of it is required.
You can see reader, there are challenges to be overcome. But challenges are the basis of engineering. Biomass could potentially provide a fully indigenous portion of future energy demand. The creation of rural jobs and the repurposing of aging powerplants are some of the benefits. Biomass fuelled power generation is a ‘carbon neutral’ form of energy. The amount of carbon absorbed by the plants during their growing cycle is the same at that released during combustion. Thus, no extra carbon gets released into the atmosphere. But what if you wanted to go a step further? What if you wanted a ‘carbon-negative’ energy source?
This is where CCS comes in.
The science is simple. Flue gases pass through a scrubbing amine solution that isolates and collects CO2. The compressed CO2 then travels, in its supercritical state, via pipeline to a subsea aquifer (cavernous rock formation suitable for carbon injection). Essentially, it is propelled back from whence it came. There are issues with CCS. The parasitic load requirement for the thermodynamic processes impacts on overall plant efficiency. It also complicates powerstation design and operation. But as with any burgeoning technology, these issues will be reduced over time. For now, biomass power generation is a workable and relatively well used technology. 100% indigenous fuelled biomass generation is the next logical step. The prospect of biomass and CCS together producing a part of the nation’s energy need is a fascinating one. It is a technology worth pursuing. Not only is it a means of achieving energy independence, it is a way of removing carbon from the atmosphere while producing electricity. How amazing is that?
Alumni of the National University of Ireland, Galway, Michael graduated with a bachelors’ degree in mechanical engineering that latterly specialised in renewable energy generation. Having spent the past six months in Canada with a micro-tunnelling company, Michael returned to pursue opportunities in the renewable sector. ‘Maximise the working efficiency of what we already have, maximise the commercial feasibility of what’s to come.’ firstname.lastname@example.org