24 November 2022

The Story So Far: Plynlimon Field Site

Find out how our project has been progressing at one of our field sites, Plynlimon in Wales.

A photo of the sheep-grazed upland grassland at our field site in Plynlimon, Mid Wales

Plynlimon in Mid-Wales is one of our three field sites, making up part of the Work Package 1: Field Sites. The field sites demonstrate and test the impacts of basalt application on greenhouse gas removal (GGR), productivity of upland grasslands and soil health.

Our Demonstrator programme has been running since May 2021, so we thought now was a good time to share the story so far on each of our research strands, beginning with our field sites. (You can read our updates from Harpenden here and North Wyke here.) We’ll then seek to provide regular updates on what’s happening in each of these areas. So, what’s been happening at Plynlimon since our funding was approved?


June - August 2021

Getting going. Staff are identified and briefed as to our project goals and requirements. A sampling design is agreed with data to be collected on soil, water, greenhouse gasses, vegetation, weather, freshwater biology and even sheep grazing patterns. Then the bespoke scientific instrumentation is identified and ordered, including two powerful off-grid renewable energy rigs of combined solar and wind. Meanwhile, new plant production exclusion cages are fabricated and installed to ensure sheep grazing does not influence the vegetation analysis. A botanical surveyor records the diversity of plant species present as a baseline to return each year to assess if there has been any change. Based on the NVC habitat classifications we find the plots in both catchments have a generally grassy vegetation with a fair cover of dwarf shrubs in places (such as bilberry [Vaccinium myrtillus] cover of 10-40% and heather [Calluna vulgaris] at 5-10%). In total around 40 species of vegetation are found on the site.

As activity increases at the site, located within the long-term Plynlimon Research Catchments,  stakeholder engagement gathers pace as the team engages with Natural Resources Wales (NRW) to ensure the environmental impact is constrained and permissions to apply crushed basalt rock are obtained.

Early on we identified some possible risks and issues to watch out for. Firstly, the lining up of supply, storage and application of rock dust in suitable weather around April at catchment scale in upland conditions will be very challenging logistically. Winter production of the basalt to 0-2mm size is very difficult for the quarry to hit a certain delivery date as the fine mesh they use to sieve the basalt can become clogged in damp conditions or the dust can simply blow away in very windy weather. Additionally, conditions at the site for storing and spreading the rock dust must be suitable for a contractor to safely get around site and keep the dust as dry as possible so it does not get jammed in the spreader hopper. These weather conditions are far from a given during early spring in upland mid Wales! Possible mitigation strategies are in discussion.

September - October 2021

Logistic discussions of applying the crushed rocks are ongoing. Plynlimon is a remote upland site, so helicopter application is a contender, initially. However, this would introduce many other challenges. Our Plan A is to apply the basalt by tractor or quad bike, but some of the slopes are steep and we do not want to risk damaging the grassland with heavy machinery. A glimmer of hope comes as Alan Radbourne makes contact with a specialist contractor who has experience applying natural aggregates on this hilly sheep farm.

November - December 2021

Unfortunately, there have been some delays following long lead times caused by a combination of Brexit and COVID. However, the weir system is now in and we’re adding further instrumentation as it arrives. Our Cardiff colleagues Nick Pidgeon and Karen Henwood have also been for a site visit.

January 2022

Good news! The contractor contacted last September has agreed to take on the crushed basalt spreading, deciding it is best to spread in May to give the land a chance to dry as much as possible before the specialist runs a tracked tractor with a light hopper across it. A quarry order is placed for 86 tonnes of crushed basalt (we have a big area to cover!) for delivery and spreading in May 2022. We will apply at a rate of 20 tonnes per hectare.

Instrumentation is being installed as it arrives. Although this process is frustratingly slow with delays in supplier lead times, as a result of bespoke systems development supply chain issues with Brexit and Covid. Some equipment we have now been waiting for over three months for. Other equipment we were quoted lead times in excess of 9 months best case scenario: needless to say, we found other suppliers. These delays are further compounded by challenges of setting up a remote upland field site in winter during short days and poor weather. For example, we had to abandon one trip to install after heavy snowfall while on site. Due to the distance to the site, which is quite remote, this is proving challenging logistically and delaying progress slightly. We’re redirecting additional staff to support the installation progress and ensure we get this completed ASAP.

Despite all this, we know that soon enough the Plynlimon field site will have all instrumentation installed and a full suite of baseline data being collected before the first application of crushed basalt.

This quarter, we’ve been doing more stakeholder engagement. Our site manager Alan Radbourne presented the Demonstrator to a UKCEH internal conference, generating lots of interest and the possibilities of collaborations forming. It’s all very exciting! Alan’s also been spending time working on our working relationships with the landowner, Natural Resources Wales and the Welsh Government to ensure all the relevant permissions are all in place, and of course to engage them in research outputs. They’ll all be very curious to see our results. The good news is all permissions to spread are provided by NRW and confirmation that the farm will not have their glastir agri-environment payments impacted. So, we are set to go!

February - March 2022

The combination of storms Dudley, Eunice and Franklin in February produce significant damage to much of our installed equipment. After over 40 years of research at Plynlimon we have never experienced such storm chaos. Fortunately, the incredible team get straight to work trying to recover from the damage, but damage to the wind turbines, weirs and GHG equipment will cause more delays in getting the site fully active.

We’ve got lots of trackers to make sure all the Demonstrator projects stay on target for the duration of our grant, so we’ve updated our part of the Gantt chart to reflect the changes that this storm damage has meant for our basalt applications. The storm damage coupled with the long delays caused by Brexit and Covid now mean that we’re just going to do two basalt applications, in May 2023 and 2024. It’s a shame, but it does mean we’re building a very robust baseline of data for a full year. The financial challenges of replacing our kit, and the staff time (which is also costed) we’ve had to spend fixing it, offset the current budget available.

During this time we complete the installation of the power systems for the automated greenhouse gas chambers, and start testing the equipment that will be measuring CO2 and methane automatically 24 hours a day every 2-3 hours with light and dark chambers. We can also capture the net ecosystem exchange of carbon and calculate the carbon balance for the site.

The weir install had just finished, but the sheer force of the storm water had washed it all out again. We know how to rebuild, installing an overflow pipe to limit pressure building to critical levels again, and hopefully after a growing season the sods of earth will knit back together as the grass re-roots, so next winter’s storms will not affect us so badly. The automatic water samplers are going in very shortly. We will collect discrete samples for analysis in the lab. We also need to install sensors for real-time pH monitoring and dissolved CO2. The pH sensors have arrived but we’re still awaiting the latter. Some of this equipment has been bought by some additional funding through a capital bid that is a great addition to the site to provide the highest quality data incoming. Most things are now ‘in the field’ in both catchments – and we should be measuring effectively very soon.

April - July 2022

We’re all set to measure! Data is beginning to come in, with full data flow scheduled to be active from May 2022, when we anticipate all site instrumentation is due to be installed, checked and active from this point on.

This quarter has also seen to cross-programme engagement with the other Demonstrators on the GGR-D Programme (CO2RE hub). We’ve been discussing with a Bangor University project looking to incorporate ERW into their tree planting experiments. Also, we’ve been discussing synergies with the GGR Peat Demonstrator to see how we might work together.

Stakeholder engagement is ongoing too. We’ve continued our engagement with local farmers at Plynlimon to understand the application and interest in ERW for upland farming systems. It’s important that interested parties like farmers and local communities are at the heart of our engagement – after all, if we’re to upscale ERW as a GGR technique, we’ll need to have the agricultural sector onboard.

August 2022

Data flow is now fully active, with all our site instrumentation installed. One gas chamber that was broken through storm damage is still to be fully replaced, so we’re awaiting instructions from the supplier on that. We are going to be trialling a new way to measure carbon dioxide sequestration, which involves measuring the mineralisation in buried bags of crushed basalt in our field site. Rock dust was sieved to the correct particle size fraction, added to nylon mesh bags and buried in the plots in the week beginning 25th July. Each year we will dig up a mesh bag and analyse the mineralisation of the basalt to see what has been happening.  

Stakeholder engagement continues too. Alan Radbourne and Jack Cosby have recorded a podcast about the Plynlimon Research Catchments, mentioning the ERW Demonstrator project, for the Ecological Continuity Trust (ECT), which is available here.

Previous risks and issues we reported have been resolved with the updated application plan and significant work to fix the issues posed by the storm damage.

Very interesting news. Watch this space for further updates on our Plynlimon field site!

With many thanks to Dr Alan Radbourne for help co-ordinating this blog

- Authored by Victoria Giordano-Bibby

Research Centre Manager