Mar Pérez-Fortes

Dr Pérez-Fortes received her Master of Science in Industrial Engineering from the Universitat Politècnica de Catalunya (UPC) in 2005. She then started her PhD at UPC, in the Centre for Process and Environment Engineering (CEPIMA) group. In 2011 she was awarded her PhD in Process System Engineering. After a Post-Doctoral period in the University of California - University of Connecticut, she joined the Joint Research Centre (JRC, in Petten) in September 2013 and since then she has been working on the techno-economic evaluation of different options of CO₂ utilisation.

Evangelos Tzimas

Evangelos leads the ‘Carbon Capture, Utilisation and Storage (CCUS)' Project of the Energy Technology Policy Outlook Unit in the Institute for Energy and Transport of the European Commission's Joint Research Centre. The aim of his work is to provide scientific and technical support for the conception, development and assessment of energy and climate policies of the Union through techno-economic assessments and targeted analysis of low-carbon energy technologies, addressing their potential, benefits and barriers to their large scale deployment. The current focus of his work is the implementation of the European Strategic Energy Technology Plan (SET-Plan).

© Fotolia

Carbon dioxide utilisation for the production of fuels, chemicals and materials has emerged as a possible complementary alternative to CO₂ storage and as a promising source of competitive advantage for European industry. In order to contribute to the on-going debate regarding the potential of CO₂ utilisation as a CO₂ mitigation tool and the competitiveness of carbon utilisation processes, the Joint Research Centre (JRC) - the European Commission’s in-house science service - has focused on the study of five products: methanol, formic acid, urea, aggregate for concrete, and polyethercarbonate polyol for polyurethanes.

The following results correspond to the findings of the JRC’s on-going study, the methodology of which is based on process system engineering. The results show that all the simulated processes are >95% efficient in terms of CO₂ conversion and entail fewer CO₂ emissions compared to their equivalent conventional processes, mainly because the carbon that would otherwise be provided by fossil fuels is provided by CO₂. The positive impact on CO₂ mitigation increases significantly when the hydrogen needed to react with CO₂ is produced using renewable electricity. In this case, hydrogen is considered to be produced in an alkaline electrolyser. The comparison of a carbon utilisation plant vs. a conventional process is made at plant level (see Figure 1).

Methanol is emerging as a viable alternative to fossil fuels in the transport sector, including the maritime sector. Its current global market is around 61 Mt/yr. The process modelled considers a catalytic reactor that combines H₂ and CO₂, and the downstream product separation steps (in flash vessels and in a distillation column). The considered plant scale is 450 kt/yr of methanol. It was found that in order to have a process that has a net consumption of CO₂ (i.e. indirect and direct emissions of CO₂ smaller than the CO₂ used as a raw material), the electrolyser has to be powered by renewables (zero emission sources).

Operating costs are higher than benefits (with electricity consumption as the main contributor), thus the NPV is negative at the current assumed market prices. The price of methanol, oxygen, CO₂ and electricity and the investment cost of the plant, have been varied one by one to analyse their influence on the NPV. It turns out that the most influential variable is the electricity price, followed by the product price. An electricity price of EUR 9/MWh (current reference price is EUR 95/MWh) or a methanol price of EUR 1,400/t (current market price is EUR 350/t) would make the investment profitable. The price of CO₂ as income for the methanol plant at which the NPV is equal to zero is EUR 670/t (the reference market price is EUR 38/t).

We have analysed the market penetration of methanol based on its annual growth in demand, the coverage of imports, its possible use in the shipping sector, its use in fuel cells and residential cooking (as stationary applications) and its use in passenger and light commercial vehicles, according to the guidelines of the Fuel Quality Directive. In 2030, around 40 Mt/yr of CO₂ may be required to meet European demand for methanol, under assumed penetration percentages and specific pathways.

Figure 1: Boundaries of the JRC analysis

Formic acid has a current global market of 0.65 Mt/yr. It is a candidate to be used as a hydrogen carrier, and so is a product that could notably increase its demand. The process modelled is composed of a catalytic reactor that combines H₂ and CO₂, and the downstream product separation steps (liquid-liquid separation and two distillation columns). The considered plant scale is 11.4 kt/yr of formic acid. As in the case of methanol, the electrolyser has to be powered by renewables to have a net consumption of CO₂.

Operating costs are higher than benefits; variable costs of consumables (catalysts, followed by solvents), electricity and steam, are the main contributors. In order to have a positive NPV, we have studied the sensitivity of the NPV to variations in the prices of formic acid, oxygen, CO₂, electricity, steam, and to the variation of the investment cost. The most important variables are consumables (particularly, specialised catalysts), formic acid and electricity prices. Prices of formic acid higher than EUR 1 600/t (current market price is EUR 650/t) would allow positive NPVs. Analogously to the methanol case, we have estimated formic acid penetration pathways. The fuel cells market as a stationary application and its use as a hydrogen carrier in the transportation sector (in fuel cell vehicles and combined with compressed natural gas) are taken into account. Its total request for CO₂ in Europe would be for 7 Mt/yr in 2030, under assumed penetration percentages and specific pathways.

Urea is the main nitrogen-based fertiliser. Moreover, its use in stationary and mobile nitrous oxide (NOx) reduction applications combined with diesel is increasing. Its current global market is around 160 Mt/yr. It is conventionally produced by the combination of CO₂ with ammonia. The CO₂ used in this process comes from the separation of H₂ and CO₂ during the ammonia synthesis process. We have studied two situations:

• Due to the stoichiometric unbalance of conventional plants that use natural gas to produce H₂ and CO, which is converted into CO₂ and separated to be used in the urea process, there is a certain amount of ammonia that is not combined with the CO₂ to produce urea. The use of this "extra" ammonia is what is known as urea yield boosting. This can increase production per plant by 5%. In our assumed plant scale (283 kt/yr), this results in a use of 0.01 Mt/yr of captured CO₂ per plant. The overall EU potential for CO₂ uptake could be in the range of 0.32 Mt/yr of CO₂.
• In order to consider all the CO₂ used for the urea process coming from a CO₂ capture plant, ammonia has to be synthesised by combining H₂ and nitrogen, with the H₂ coming from electrolysis. The process, similar to the methanol and formic acid case studies, needs renewables to power the electrolyser. Operating costs are higher than benefits, with electricity as the main cost element. The sensitivity of the NPV to variations in the prices of urea, oxygen, CO₂, electricity, and to the variation of the investment cost, demonstrates that the main influencing variables are electricity, investment cost and the price of urea. An NPV equal to zero is obtained when the urea price is EUR 1 400/t (the reference market price is EUR 245/t) or CO₂ income equals to EUR 1 550/t. The European urea market growth up to 2030 would imply a CO₂ demand of 7 Mt/yr.

Calcium carbonate and polyols syntheses do not require hydrogen to be combined with CO₂. In the particular case of aggregates, fly ash and/or other alkali residues are used as feedstock. The prime market for aggregates is the building sector. Concrete is the most widely used construction material: it is estimated that the average consumption is 1 t/yr per person. The global output of fly ash is around 800 Mt/yr, approximately half of which is disposed of as a waste product. The global market for polyols is about 6.7 Mt/yr. The simulated plants are of 100 kt/yr of aggregates and 120 kt/yr of polyol. Preliminary results show that both processes have positive NPVs. Optimisation of process conditions could help decrease the pay-back periods and attract stakeholders into CO₂ utilisation as a new business proposition. Market penetration, taking into account growth of the polyols market in Europe, could imply a demand of 0.12 Mt/yr of CO₂. The results for the ammonia-urea process and for calcium carbonate and polyols syntheses are under review and the calculation of the CO₂ demand for aggregates is still ongoing.

Overall, according to the selected processes in this work, and according to the assumed hypotheses, the CO₂ utilisation potential by 2030 could reach 55 Mt/yr of CO₂, assuming a number of optimistic penetration pathways for the methanol and hydrogen economies that are not yet broadly developed. As a matter of comparison, the Boundary Dam Carbon Capture and Storage Project (Canada) has a capture capacity of 1 Mt/yr of CO₂. For processes that consume H₂ as a raw material, it is crucial to power electrolysis by renewable sources. As it has been depicted in this article, different favourable conditions may help the various technologies to reach or to enhance their profitability, and a combination of them is desirable. What is common to all is: lower electricity and steam prices (also, better plant integration) and higher prices per tonne of CO₂ and/or for products synthesised from CO₂ are needed.

R&D is also crucial to decrease operating costs, especially in the use of catalysts. Carbon utilisation processes provide a net contribution to CO₂ emissions reduction. However, the context and the "supply chain" are not yet in place. The context, i.e. legislation and regulations, should take into account products made from carbon dioxide (as the recent Renewable Energy Directive/Fuel Quality Directive is paving the way to fuels synthesised from CO₂). At present, however, CO₂ fuels and products are not fully defined in regulation. As regards the supply chain, carbon dioxide to be used in different utilisation processes varies in terms of its purity (thus, the availability cost). For instance, methanol synthesis should use a pure stream, while mineralisation can even be used as a capture method.

This is also a criterion for CO₂ utilisation movers, when selecting their source of CO₂. Due to the costs incurred in CO₂ capture plants in power plants or heavy industry processes, the CO₂ utilisation investor may be attracted by other purer and/or cheaper CO₂ sources (for instance, those derived from biomass processes or from CO₂ capture from the atmosphere). Therefore, measures to motivate the use of CO₂ coming from power plants and heavy industries need to be put in place if the aim is to support a combination of CCS and carbon utilisation processes. Moreover, such CO₂ utilisation processes that consume H₂ as a raw material will benefit from specific renewable/energy storage advancements.

For further information please visit: https://setis.ec.europa.eu/publications/jrc-setis-reports