From Coal to Biomass with JS Ewers 

 Last month a group of 20 people descended on Nelson at the invitation of JS Ewers to see and hear about the process this horticulture business has been following to decarbonise. This is a journey that began in 2017 with a chance conversation with a supplier who had installed a biomass boiler a few years prior. The conversation covered the increasing cost of fuel, and the ETS. This soon led to a heating expert conducting an audit on JS Ewers energy use.

The audit led to a 3 staged approach to decarbonising the business. Step 1 was to try to reduce the energy that they were already using. Several measures were put in place to ensure the existing boilers ran at maximum efficiency; This led to the installation of:

• 6 hectares of thermal screens
• flow meters
• 3 kms of underground pipework
• a main ring buffer tank which allowed the storage of hot water with minimal heat loss rather than firing up the boiler when the greenhouse temperature dropped

All of these actions lead to a reduction in the amount of energy that JS Ewers required to operate their greenhouses which in turn meant that they had a really good idea of how big and how many boilers were required on a day to day basis.

The ne stage was broken down to 2 separate projects due to the nature of the JS Ewers being spread over more than one site. For the smaller site, the 40-year-old coal boilers would be converted to take wood pellets. The larger site though would have 2 brand new biomass boilers installed from Europe. We were lucky enough to see both of these changes but particular focus was given to the coal conversions as this is a much more accessible way to decarbonise for smaller growers due to the lower costs involved.

Pierre Gargiulo kindly talked through the measures taken to reduce the risk of burn back, a recognised problem with these types of conversions, however, one that is mitigated with a range of safety features.

There were lots of positives that the growers present were able to hear about, most notably:

• The safety measures have worked on the occasions that wood burn could have been a problem
• Wood pellets are much cleaner than coal
• As a result, the boiler runs much cleaner and requires less maintenance and therefore less expense
• They have learnt that coal to wood pellet use is 1:1 so the need for huge storage bunkers isn’t necessary
• And of course wood pellets are ETS free due to being carbon neutral

This is still a learning journey though with Creosol being produced if the boiler isn’t quite tuned correctly.

Some points to consider if you’re thinking about a boiler conversion:

• The conversion from a waste oil boiler to using wood pellets, isn’t as easy because the auger will have been removed and this is crucial for wood pellets. You could potentially look to source an old coal boiler with all the parts as a workaround
• While wood pellet supply in the South Island is good, you will need to get a representative on your site to talk about the cost of delivering to you – obviously the further your business is from the producer, the more the cost of the wood pellets.
• You will need a covered area for storing the wood pellets which is big enough for them to be tip loaded to drop into the feed system

A representative from Azwood was on hand to answer questions about South Island biomass and wood chip, while North Island growers could contact Nature’s Flame to find out about costs and supply.

In terms of the screens that JS Ewers had retrofitted in 2021, the advice given was to research and talk to suppliers about your particular set up as greenhouses will require screens for different reasons such as just saving energy or offering some shading cover as well. Again the screens have required a learning process to make maximum use of the available controls to manage humidity (and potential fungal issues) and to ensure that opening the screens in the morning don’t mean a sudden, large increase in the atmospheric temperature. One lesson learnt was arranging for retrofitted screens to be installed when there is no crop in the greenhouse would definitely be advantageous!

None of these projects would have been possible without co-funding from EECA through the GIDI fund, which JS Ewers applied for when it started in 2020.

 converted coal boiler now firing on wood chip 

Inside a biomass boiler

The hydraulics operating the new biomass boiler

upgraded coal storage for wood chip