Sustainable energy

Energy_webCarbon dioxide options for commercial greenhouses

The changing landscape of fossil fuels presents increasing business risks for Australian domestic industrial and commercial energy consumers. Rising costs and uncertain supply of natural gas (1) and the existing high price of Liquid Petroleum Gas (LPG) represent a significant portion of this risk. Adding complexity to this changing landscape is mounting international pressure on Australian policy makers to replace fossil-fuelled energy with renewable alternatives. Horticulturists use natural gas and LPG for greenhouse environment management and as a result are left exposed to an uncertain future.

The primary source of heating in commercial greenhouses is typically combustion of coal or biomass. This heating is inexpensive, reliable and simple to operate and maintain. The cost of heating energy derived from coal and biomass is in the order of $4 to $5 per gigajoule. The cost of heating energy derived from natural gas and LPG is approximately $13 and $22 per gigajoule respectively.

The use of natural gas and LPG in commercial greenhouses is primarily for carbon dioxide (CO2) enrichment. The cost of this practice is very high but the benefits to crop growth and yield justify this high cost. Identifying cheaper and reliable sources of CO2 could have significant financial benefits for those horticulturists that apply CO2 enrichment practices as well as reduce reliance on fossil fuels. Potential sources include waste from industrial coal and natural gas combustion (such as energy generation) as well as the flue of coal and biomass furnaces used for heating commercial greenhouses.

Figure 2.32: Schematic showing the effect on extreme temperatures when (a) the mean temperature increases, (b) the variance increases, and (c) when both the mean and variance increase for a normal distribution of temperature.

Figure 2.32: Schematic showing the effect on extreme
temperatures when (a) the mean temperature increases, (b) the variance increases, and (c) when both the mean and variance increase for a normal distribution of temperature.

Climate change science
The science behind climate change is proven and freely available from the Intergovernmental Panel on Climate Change (IPCC) (2). However, most of it is written and presented by scientists for use by other scientists, limiting its value for informing operational and strategic business decisions. Figure 2.32 from the IPCC Third Assessment Report (3) is an exception. It shows a typical Bell Curve for any collection of temperature measurements: the average temperature is at the top of the Bell Curve, low temperatures are at the left and high temperatures are at the right. The effects of increased concentrations of atmospheric carbon dioxide, methane and other greenhouse gasses shifts the position and shape of this Bell Curve. The graphic shows an increase in the mean (or average) temperature (chart a) and an increase in the variability in temperatures (chart b). The combined effect (chart c) shows that minimum temperatures change only slightly but the maximum temperatures are higher and the number of hot days increases. A 2OC increase in average temperature translates to significantly more change to maximum temperatures.

This effect is already evident in the record temperatures set in both hemispheres in recent summers (4,5). The consequences can be seen in the abandonment of towns and villages due to sea water innundation (6) as well as the increasing intensity and frequency of bushfires (7). Globally, these changes are presenting significant challenges to governments (8,9).

Australia’s response
Australia’s response to climate change and global warming is adding complexity and uncertainty to changes in the energy landscape. International pressure to reduce our reliance on coal-derived energy, such as that exhibited at the G20 summit (10) and the recent Paris conference (11), has been applied to Australian policy makers. However, Australian leaders have been slow to accept climate change and the response to it has been inconsistent, particularly with respect to Australia’s continued reliance on fossil fuels (12).

This inconsistent approach is demonstrated by implementation and then scrapping of a price on carbon dioxide emissions (13). The debate on the Renewable Energy Target (14) had a detrimental effect on the investment into renewable energy. Existing legislation and policy such as Carbon Credits (Carbon Farming Initiative) Act 2011 and the Direct Action Emissions Reduction Fund (15) supports soil carbon sequestration (16) and clean coal technologies (17) but has little or no applicability to horticultural emissions such as the reliance on gas for CO2 enrichment.

The use of protected cropping practices is a form of climate change adaptation. However, these practices need continued modification to prepare for a changing climate, particularly in response to rising temperatures and increasing fuel costs. Modification of protected cropping practices to accommodate climate change has the potential to create opportunities for strengthening the business viability of horticulture and augmenting food security for domestic consumption and export.

Horticulturists have options for reducing reliance on fossil fuels and adapting to climate change. Most of these options, however, have low or no appeal due to relative cost (such as heat pumps and wind power), complexity (generating syngas from industrial or agricultural processes) or physical footprint (such as solar energy collection). Industrial symbioses (using waste CO2 from industrial processes) also have low applicability due to the continued placement of greenhouses in regional areas as opposed to locating them adjacent to sources of waste heat and carbon dioxide.
Those remaining options for adapting further to climate change require an innovative approach to testing and integration and include:

  • Using the combustion of natural gas and LPG not only as a source of CO2 but to also power absorption refrigeration plant (18). This would not only provide continued supply of CO2 for enrichment but allow longer exposure times without the need for venting greenhouses.
  • Cleaning the CO2 emitted from the flue of existing coal and biomass furnaces (19,20) and using this for enrichment. This solution has the potential to make the combustion of expensive natural gas and LPG a secondary source of CO2 for enrichment.
  • Locate new greenhouses adjacent to sources of waste heat and CO2.
  • Perform an assessment of the total volume of CO2 consumed by commercial greenhouses (existing and potential) in Australia in order to inform climate change policy development and recognise horticulture as a legitimate consumer of CO2.
  • Develop tools and methods that simplify the calculation of the true cost of CO2 enrichment so that the efficiency of this practice can be improved.

Climate change will require a response from all commerce and industry. Horticulturists have the choice to either wait for the risks or prepare for the opportunities.

About the author
Ian has worked in a variety of technical fields, including satellite and terrestrial communications, scientific instrumentation design and manufacture and information management. The practical knowledge developed during these experiences has been strengthened with qualifications in science, engineering, business informatics and energy. His broad knowledge and experience allows Ian to see the potential for new or improved connections across isolated process, disciplines and industries. This perspective was applied most recently in a research project designed to identify ways in which commercial greenhouses could reduce risk and cut costs by moving away from fossil fuels such as natural gas and LPG. Ian is currently pursuing a number of sustainability-related projects in plastic waste and carbon dioxide management. Email:

Reference List

(1) Wood, T.; Blowers, D.; Chisholm, C. Gas at the Crossroads Australia’s Hard Choice: Melbourne, 2014.

(2) Intergovernmental Panel on Climate Change.

(3) IPCC. Third Assessment Report – Working Group 1: The Scientific Basis (chapter 2) 2001.

(4) Samenow, J. Heat records all over: The Northern Hemisphere is in hot water. The Washington Post, 8 July 2015.

(5) Flack, N.: 2015 likely to be Warmest on Record, 2011-2015 Warmest Five Year Period. United Nations Information Centre: Canberra.

(6) Smith, R. Small Alaskan island Kivalina expected to be covered by water within 10 years. 31 August 2015.

(7) Hughes, L.; Steffen, W.; Pearce, A. The heat is on: climate change, extreme heat and bushfires in WA, 16 March 2015.

(8) Davey, M. Lack of planning for climate change puts Australia behind its allies, report finds. The Guardian, 22 September 2015

(9) Whittington, E. How well prepared are businesses for climate change? The Conversation, 5 March 2015

(10) Lewis, R. Shorten: Barack Obama shirt fronted Tony Abbott on climate. The Australian, 16 November 2014.

(11) COP21: Turnbull pledges $1 billion to battle climate change. SBS News.

(12) Ricci, C. Tony Abbott’s climate change policy goes global The Sydney Morning Herald, 30 November 2014.

(13) Carbon tax: a timeline of its tortuous history in Australia. (accessed 17 June 2015).

(14) Australian climate change policy: a chronology. (accessed 18 July 2015).

(15) CER: Emissions Reduction Fund methods. 2015.

(16) Carbon Farming Initiative Amendment Bill 2014. In 23 2014–15, 2014.

(17) Barrow, J. Fact check: Can clean coal technology halve emissions within 5 years? ABC News, 14 November 2014.

(18) Alsaqoor, S.; AlQdah, K. Performance of a Refrigeration Absorption Cycle Driven by Different Power Sources. Smart Grid and Renewable Energy 2014, 161-169.

(19) Dion, L.-M.; Lefsrud, M.; Orsat, V. Review of CO2 recovery methods from the exhaust gas of biomass heating systems for safe enrichment in greenhouses. Biomass and Bioenergy 2011, 35, 3422-3432.

(20) Roy, Y.; Lefsrud, M.; Orsat, V.; Filion, F.; Bouchard, J.; Nguyen, Q.; Dion, L.-M.; Glover, A.; Madadian, E.; Lee, C. P. Biomass combustion for greenhouse carbon dioxide enrichment. Biomass and Bioenergy 2014, 66, 186-196.  Ω

PH&G January 2016 / Issue 163