Carbon capture and storage/utilisation
Two thirds of our emissions are process emissions linked to a reaction that happens when limestone is heated. Even if all kilns were optimised and the fuels mix perfect, emissions would still be substantial.
Carbon capture and storage or carbon capture and utilisation represent the measures with the biggest abatement potential of all, and are, in fact, the only ones tackling process emissions during the manufacture of lime products.
Its costs are high in comparison with the production costs of lime. Given the right technological development, economic situation and infrastructural requirements, and with an incentive to not harm the EU lime industries competitive position, the industry would embrace this technology.
If capturing carbon is the key to substantially lower emissions, it does represent a real challenge in terms of cost.
In 2012, TNO (Netherlands Organisation for Applied Scientific Research) performed a techno-economic evaluation of post combustion CO2 capture in lime production plants. Using the lowest electricity price assumed in the report, costs to capture CO2 were evaluated at €94/tonne of avoided CO2.
Future innovation could provide the potential to reduce the cost associated with capturing CO2 and quick uptake would accelerate innovation. Nevertheless, at current price levels, it is not economically viable since it would be more than double the production cost.
Storage or utilisation?
Assuming that the barriers of technical and economic feasibility as well as social acceptance have been overcome, the other big question is what to do with captured CO2. Two options are available: storage or utilisation.
Storage involves transporting the CO2 to a geographically suitable location and storing it underground. Currently, lime plants are typically located right next to the limestone quarry, not clustered in large industrial agglomerations. Transport costs – to overcome the distance between the lime plant where it is captured and the location where it is stored – as well as any additional piping infrastructure can add significantly to the capture costs. Storage locations would need to be developed and maintained and public and regulatory acceptance of CO2 storage still needs to be overcome.
The business case for capturing carbon, could be improved in case the captured CO2 could be used, rather than stored. Storage costs could be saved, and it might get a financial value. The lime industry itself will not be able to use it, but the business case to capture the CO2 could benefit from others using it. A lot of research is currently devoted to developing new uses of CO2, including:
- Using it to produce fuels/hydrocarbons.
- Transforming CO2 into inert carbonates, to be used, for example, as construction material.
- Using it as a feedstock for the production of polymers.
- Applying CO2 to enhance recovery of fossil fuels (oil, gas).
Many of these applications are, however, only at research stage for the moment.
Although not a traditional abatement measure, and not within the scope of our analysis, it is important to note that during the lifetime of products in which lime is applied, CO2 from the atmosphere is captured (basically reversing the reaction in which lime is produced from limestone).
If atmospheric CO2 has good access to the material, as is the case for example in some building materials, the lime, or the new material can reabsorb CO2. This so-called “carbonation” partly closes the loop starting with CO2 process emissions during lime production.
Carbonation is highly dependent on the application; in some applications the main carbonation takes place within five years, in other applications it takes longer. For example, for lime mortars, it is estimated that within 100 years, 80 – 92% carbonation will take place.
Pathway to 2050
Taking into account the unique emission profile of the lime industry, the type of plants in operation today and the possible savings, we have mapped a possible carbon reduction roadmap from 2010 to 2030 and 2050.
A reduction of emissions related to the heat production in kilns can be achieved through a reduction in fuel intensity and switching to lower carbon fuels whilst a reduction in process emissions can only be achieved using CCS/CCU.
The technical potential of these options is shown by arrows with a colour gradient, representing the huge uncertainty in the potential that could be realised in 2030 and 2050. It should be kept in mind that this technical potential is intended as a theoretical thought experiment, and does not necessarily reflect a possible reality or economical potential.
The figure shows two options for switching to lower carbon fuels:
- A fuel switch from fossil solid fuels to gas in 2030 and 2050.
- A full decarbonisation of the fuel mix, for example by using biomass (in 2050).
These options are shown as the yellow arrows. The last (red) arrow represents the technical potential of carbon capture and storage/utilisation. This technique could bring about the biggest reduction in emissions. However, it is important to understand the barriers related to CCS/CCU.
When assessing the effect of the remaining carbon emissions, the mechanism of natural carbonation could be taken into consideration.
This is an extract from the report 'A Competitive and Efficient Lime Industry' published by the European Lime Association.
Read the article online at: https://www.worldcement.com/special-reports/06012015/a-competitive-and-efficient-lime-industry-part-three-86/