Synthetic ammonia production relies heavily on the Haber-Bosch process, fixing nitrogen with hydrogen to produce ammonia for use as a fertiliser. Worldwide ammonia production accounts for 1-2 per cent of global energy consumption and 3-5 per cent of natural gas production. The Haber-Bosch process uses 7.9kWh to produce each 1kg of ammonia. In Queensland, roughly 0.89kg of nitrogen is removed from the soil for each tonne of cane harvested

Whilst fertiliser use at this site is very minimal in comparison to global consumption, it is doing its part by reducing application rates, capturing runoff, storing and reusing the nutrient rich water which all aid in protecting the Great Barrier Reef. In separate trials the farm is using various fertiliser types such as slow release at reduced rates to establish beneficial effects on yield. These efforts reduce the site’s indirect energy use and carbon footprint.

The site produces around 124 Tc/Ha using three pumps, consuming 34,832 kWh at a cost of $11,692 per annum, corresponding to 80% of total annual site consumption, which is 43,472 kWh. A recent energy audit made recommendations that showed the site has the potential to reduce its direct consumption and build on efforts from the Queensland Farmers’ Federation Reef Alliance program.

Table 1. Current energy use for irrigation

The farms focus is on improving the efficiency of the pumping system. The audit identified that pump one is operating below its best efficiency point due to suspected cavitation damage and is limiting the output of the irrigation system. The main irrigation line is also not large enough causing an increase in pressure and reducing flow.

The audit recommended:

1. Upgrading the main irrigation line to reduce friction losses and improve flow rates;
2. Replacing a pump and adding a variable speed drive;
3. Automating the irrigation system; and
4. Changing from obsolete tariffs to Tariffs 20 and 33.

The pump upgrade will allow the irrigation system to increase irrigation from 619ML to 800ML/annum.

Upgrading the main irrigation line, and the pump upgrade will increase flow into the field and reduce areas of water logging by moving water through the field faster, meaning that irrigation can be managed within tariff windows. The increase in system capacity will mean less water stress on the cane while the new automation system will mean that water can be applied at the right time, further reducing runoff and infiltration losses. Implementing the audit recommendations will lead to energy, financial, and water savings, and provide a host of indirect opportunities onsite.

Table 2. Recommendations showing energy and cost savings using two pumping scenarios.

Upgrading Pump One could reduce energy consumption by approximately 27 per cent, saving around $2,079 p.a when 619 megalitres of water is pumped. If the volume of water is increased to 800 megalitres then the energy consumption will be reduced by 35 per cent, and savings will increase to $2,688 p.a.

Further, pumps one and three are currently on obsolete tariffs and Pump Two is on T20. The audit recommended to move all pumps to tariffs to 33 and 20.

Adding an automation system will allow pumping energy to be optimised by applying the right amount of irrigation at the right time to maximise production and take account of tariffs. When combined with end of field monitoring, automation has been found to provide up to a 20 per cent saving in the volume pumped for the current crop.

Plus, there is a potential to increase crop yield through improved irrigation scheduling tools. Combined tariff savings of $3,467 could be achieved from installation of recommendations in the audit while automation will reduce the annual energy usage by 34 per cent and 44 per cent when pumping at 619, and 800 megalitres of water respectively. Overall, increasing the water delivered could result in a production increase of 5Tc/Ha with additional profit of $13,825p.a. bringing the payback down for the project to 3.6 years.

By implementing all the recommendations in an 800 ML pumping scenario, energy savings can achieve 61% of total consumption, offsetting 176% of energy costs and with emission reductions of 21.5 tCO2-e per year.

Energy, water, and farming practices are all interconnected with energy use. An energy audit provides great insight for a business to cut costs and boost productivity.

Technology is changing and even with the current ‘low-tech’ GDOT monitors onsite there are improvements to be made. When asked about why they had installed monitors the farm owner said, “We need to be ahead of the game,” and by implementing a combination of the recommendations in the audit, and by participating in the Reef and Energy Savers programs it is providing the benchmarks for the region and is well placed as leading sustainable enterprise.

With the farm looking to reduce fertiliser use to a minimum while increasing yield, further indirect energy savings could be realised, provide additional savings and increased profit. The results from the fertiliser trials and implementation of the energy saving measures are yet to be finalised, as they come to light this case study will be updated.

An energy audit is a good investment

An energy audit is a great way for a business to cut costs and boost productivity.

The Energy Savers Plus Extension Program was delivered in by the Queensland Farmers' Federation with support and funding from the Queensland Department of Energy and Public Works.