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Appendix B: CO2 as a feedstock for urea yield boosting
The global agricultural industry is highly dependent on the supply of inorganic, fossil derived fertilisers to ensure adequate crop yields. Food shortages already exist globally but without the addition of fertilisers to agricultural land current monocrop plantations would not be able to meet the demand of today’s world food market.
The three main constituents of inorganic fertiliser are nitrogen (N), phosphorous (P) and potassium (K), commonly marketed as NPK fertilisers and including smaller amounts of other nutrients.
Urea is one of the most common forms of solid nitrogen fertiliser. Urea is produced by the reaction between ammonia and CO2. This is a two step process where the ammonia and carbon dioxide react to form ammonium carbamate which is then dehydrated to urea. The final product is a prilled or granulated solid which once applied to agricultural land reacts with water to release the CO2 and ammonia. The CO2 returns to atmosphere and the ammonia decomposes further to supply nitrogen at the correct rate to the crops.
Urea can also be used to produce urea-ammonium nitrate (UAN) one of the most common forms of liquid fertiliser.
Urea is a feedstock to a range of other industries, including the chemical industry, and around 10 per cent of urea produced globally will be processed to products such as animal feed, formaldehyde resins, melamine, and adhesives.
Urea has been produced on an industrial scale for over 40 years. CO2 capture plants for urea yield boosting have been installed since late 1990’s. The technology is relatively mature.
Urea production is carried out on a very large industrial scale. The size of plant is constrained only by the size of the upstream ammonia facility. A typical plant may produce 1,500 tonnes of urea per day, with systems up to 5,000 tonnes per day considered feasible. However, surplus ammonia from natural-gas based plants may be in the range 5 per cent–10 per cent. Consequently, capture plants installed for this purpose will continue to be <1000tpd in size. Coal-based urea production facilities produce surplus CO2 and are a source of rather than a sink for captured CO2.
Research into urea production is focused on enhancing the efficiency of the process to improve conversion rates, to reduce energy consumption, to reduce atmospheric emissions of ammonia and to reduce waste by-products in order to reduce production costs.
The production of urea consumes CO2 at the rate of 0.735–0.75 tonnes of CO2 for every tonne of urea produced.
The CO2 source for urea yield boosting is typically from capture plant installed on site to capture CO2 from the reformer flue gas. Urea production is inherently linked to ammonia production. Urea plants are generally located adjacent to or in proximity to an ammonia plant and close to major sources of natural gas.
In 2009 154.9 Mt of urea was produced globally. This equates to approximately 116.2Mt of CO2 feedstock used. However, this is generally captive CO2. The component of non-captive CO2 is relatively small.
Once applied to the land and contacted with water the reaction used to form urea is reversed, The ammonia produced is absorbed by the plants and the resultant CO2 is released to atmosphere, meaning CO2 is not sequestered. The permanence of storage for CO2 contained in urea which is further processed for example in the chemical industry is dependent on the process and the nature of the final product, this however accounts for a small amount of urea use.
Market analysts estimate that 187 million tonnes of urea fertiliser consumption is expected by the end of 2013–14. Much of the growth is expected to take place in South Asia and East Asia, where demand will propel more than 60 per cent of the world’s fertiliser growth.7
Size of market
According to the International Fertiliser Association the current market for urea is 159.4Mtpa (equivalent to approximately 119.6Mtpa CO2).
The commercial and economic feasibility of the technology is likely to be affected by the relative prices and demand of ammonia and urea. For example, if the demand (and price) of urea is strong relative to ammonia then there is likely to be an incentive to convert the surplus ammonia to urea using recovered CO2 through this technology. At present global ammonia is trading at prices in the region of US$350-US$425/tonne and urea at US$205-US$285/tonne. However, The volatility in the price and demand of each of these markets will impact the long term feasibility of implementing this technology
Level of investment required (to advance the technology)
As an already commercial technology, additional investment to advance the technology is not a necessity. However, R&D is likely to continue based solely on commercial drivers, with the aim of decreasing CO2 capture plant capital and operational costs.
Potential for revenue generation
The revenue potential will be dependent on the relative market prices of urea and ammonia, and the costs associated with the CO2 capture technology.
As noted above, viability and the magnitude of revenue will be sensitive to the relative prices and demand of both urea and ammonia.
The commercial benefit of the technology is likely to be limited by the comparative costs of producing urea using this technology over traditional methods.
Urea yield boosting represents a currently commercial application of CO2 capture technology.
The main barriers associated with the deployment of urea yield boosting technology include:
- Volatility in the relative price and demand for urea and ammonia making long term appraisal difficult.
- The potential high capital costs of CO2 capture infrastructure.
7 Fertilizer Demand Most Likely to Bounce Back in 2010 (September 2009) http://www.glgroup.com/News/Fertilizer-Demand-Most-Likely-To-Bounce-Back-in–2010-43308.html