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Lower-Emission Drying of Rice Paddy
Sunrice
Background/ Context
Australian Grain Storage (AGS) is the commodity storage arm of Ricegrowers Limited. SunRice is the consumer brand and trading name of Ricegrowers Limited, which is one of the largest rice food companies in the world and one of Australia's leading branded food exporters. SunRice Group Ltd is an Australian Securities Exchange (ASX) listed company.
SunRice sources rice globally. Rice sourced from Australia is grown in the Riverina region of New South Wales. The area has hot and dry summers, and availability of water for controlled flooding of rice fields that is conducive for high yields and quality rice production. Their operations in the Riverina are an integral part of the local economy, supporting rural communities and contributing significantly to Australia's agricultural exports.
Rice processing in Australia follows a series of steps designed to process raw rice grains into a product that is safe for consumption, has a long shelf life, and meets consumer quality expectations. Here is a general overview of the rice processing steps:
- Cleaning – The harvested rice (or paddy rice) is cleaned to remove any impurities.
- Drying – Drying aims to reduce the moisture content of the paddy rice – delivered to AGS at 22% – to a level suitable for storage, which is usually 14%. If rice is not dried properly, it can lead to fungal growth and spoilage. In Australia, rice drying is commonly through mechanical dryers that provide a controlled environment for faster and more uniform drying.
- Hulling, Milling, Grading and Sorting – The outer husks are removed. Then the rice is milled to remove the bran layers, turning brown rice into white rice. Finally, the milled rice is then graded and sorted based on size, shape, and quality.
Efficient drying not only preserves the rice for longer periods but also ensures that the quality of the rice meets both domestic and international standards.
Drying is one of the more energy-intensive steps in the rice processing chain, primarily because removing moisture from the grains requires significant amounts of heat and air movement. This is expensive and increases Scope 2 emissions.
Also, drying occurs directly after harvest, meaning significant quantities of electricity are consumed in a four-to-six month window from April each year.
How might we reduce the emissions and costs arising from drying rice paddy?
How might we reduce the emissions and costs arising from drying rice paddy?
There are two probable approaches:
- Improving efficiency of the drying process
- Increasing the use of renewables
Mechanical dryers can be very energy-intensive, especially those that use hot air blown through the rice to evaporate water. The source of heat also impacts the overall energy consumption and efficiency of the drying process. More efficient dryers can reduce energy consumption by optimising heat and air flow, and by recycling heated air.
Using renewables, such as solar and wind, can also significantly reduce Scope 2 emissions. If accompanied by battery storage, the stored energy can be used to power the 24/7 drying operations during periods of low or no renewable energy generation. The energy supply is also more stable and less dependent on grid electricity.
There are 13 AGS sites distributed across the Riverina region, so energy consumption is not centralised, and these sites are often in remote locations. The electricity consumption peaks significantly from a baseline of approximately 400 MWh per month across all sites to approximately 6,000 MWh per month across all sites between April and September (dependent on the harvest window).
Requirements
The solution should:
- Be easily retrofitted into existing AGS infrastructure; and
- Enable drying to occur 24/7.
Additional Information
Info Session
Check out the recording from our Info Session, where SunRice shared more about their challenge statement.
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