Case Study - Grantstown Nurseries
A switch to natural gas leads to reduced costs and emissions with increase in productivity
Located in Ballygunner, Co. Waterford, Grantstown Nurseries is a family run business with a tradition of innovation and the highest quality horticultural practices. The nursery's indoor glassed area covers one hectare and produces up to 400 tonnes of tomatoes per year.
The Currid family has been a supplier of a wide range of fresh fruit and vegetables for several decades. The tomatoes grown at Grantsown are picked, packed and delivered the same day to several major retail chains.
Up until the end of 2014, when they switched from oil to natural gas, Grantstown Nurseries had been using oil for 36 years. The nursery was originally powered by an oil burner and an analysis in 2011 showed significant potential advantages in switching to natural gas including;
- Cost savings;
- Environmental benefits;
- Productivity increases;
- Operation efficiencies; and
- Storage savings.
Natural Gas Installation Process
The existing equipment included a medium fuel oil (MFO) boiler that was suitable for conversion to natural gas, only requiring a change to the burner unit.
Description of Plant Energy Facilities
There is one main boiler-house on site with total boiler output of 3,000 kW. The boiler heats up the water which is then passed to the storage tank where it is recirculated at the required temperature until it is needed. During the day the boiler is used while at night the heated water from the storage tank is used to keep the temperature in the growing areas constant. The whole process is controlled automatically by a computer system which monitors the internal and external conditions.
Integration
A connection to the natural gas network was provided to an agreed meter location and a supply was taken from the meter and brought to the boiler-house, through the downstream pipework installed by Grantstown Nurseries.
Benefits of Natural Gas over Oil
Carbon Dioxide Capture
Tomatoes require a source of carbon dioxide (CO2) during production. In the previous process there was a requirement for purchase and storage of CO2, and at least one delivery per week. This resulted in extra ordering, storage and delivery costs. Following the switch to natural gas as the primary energy source, CO2 is now captured from the boiler flue gas, meaning there is no longer a need to order or store CO2. This also means that overall, the nursery has a net carbon output of zero. The CO2 is taken from the boiler and pumped around the nursery via a plastic piping system. This system has pinhole exits at specific intervals to allow enough CO2 to reach each plant. The facility already takes advantage of lean and organic production by avoiding the use of insecticides, and now the reuse of CO2 to aid tomato growth illustrates Grantstown Nurseries’ drive for green production.
Cleaner Windows
Particulate matter is the term for a mixture of solid particles and liquid droplets. The use of an oil based system produces more particulate matter in comparison to the use of a natural gas system. Previously the greenhouse windows required cleaning every year because of the emissions from the oil burning process. Because natural gas is a cleaner fuel the windows require less cleaning. This results in not only a reduction in labour costs to clean these specialist windows but also an increase in production due to
the additional light that is available.
Grantstown Nurseries Technical Details
| Comparisons | Percentage/Numberical Values (Annually) |
| Payback period | 2 years |
| Efficiency increase | 20% |
| Cost savings per year | €100,000 |
| Carbon reduction per year | 976 tonnes |
"The move to natural gas has been fantastic. It was a big decision to make the switch to natural gas, however this is the best system that we have ever introduced. It allows for greater efficiencies, lower running costs and significant environmental benefits. It has allowed the capture of carbon dioxide, reduced maintenance and maintenance costs and ensures cleaner glass in the growing areas. Had I known natural gas would offer so many benefits I would have switched sooner."