Clearing the Air – Drilling’s contribution to clean air?

May 16, 2022

If the UK is to meet the government’s ambitious Net Zero Strategy for decarbonising all sectors of the UK economy to net zero target by 2050, the drilling industry, as an important part of the ground engineering and geotechnical sector, must play its part.

At the British Drilling Association’s (BDA) recent seminar, ‘Drilling in Support of a Net Zero Scotland by 2045’, enthusiasm for the sector’s willingness to embrace low-carbon technologies and methodologies was clearly demonstrated. It looked at the contributions the drilling industry is making to low carbon energy schemes, and some of the routes that the sector is taking to reduce its own emissions, which was addressed in the presentation by Dave Nevey (Managing Director Eijkelkamp Fraste UK) – ‘Drilling Rigs – The Future’.

The low-emission benefits of modern rigs were undeniable, but whilst new modern rigs can potentially contribute to lowering emissions, the shift to these rigs is not without its problems. The biggest issue is the famous durability of a portion of drilling equipment and ancillaries, which means the replacement or upgrading of old plant to new more modern equipment; with low-emission up-to-date diesel engines, is moving slowly.

A recent study by Atkins / Anglian Water found that a typical site investigation comprising ten boreholes and ten trial pits produced the following CO2 emissions:

Activity Carbon Emissions (kgC02e)
Borehole – drilling with diesel cable percussion rig 811
Borehole – driving to site 509

 

Trial pits – JCB 3CX 400

 

Trial pits – driving to site 127

Following the optimisation of the scope for the GI to ensure that any existing information reduces the requirement for new boreholes, and low carbon materials in the installation and backfill are put to effective use,  the highest emissions are from the drilling rig. It is worth noting that for deeper boreholes or different strata there may be required a much larger engine than the 15kw cable percussion rig here, which drives emissions even higher. So, what can we do?

Our friends electric

Like has happened with so many other fossil-fuelled vehicles and machines, the obvious solution would be to electrify rigs. In fact, in the mining and tunnelling industries electric drilling rigs have been used for years, but hardly at all above ground. However, BDA Member and dewatering contractor WJ Groundwater has been operating an electric drilling machine since 2020. Managing Director Richard Fielden says: ‘We wanted to offer all our customers a zero-emissions drilling option. We extensively use specialist rigs in a tunnelling environment where mains electricity is readily available, so procuring an electric powered multi-functional drilling rig was an obvious choice to fulfil our requirements for tunnelling related projects and in a traditional non-tunnelling construction site environment’.

WJ worked with the Italian manufacturer Comacchio, to specify an MC6 drilling rig equipped with an 87kw electric motor and a 7.3kw ‘slave’ diesel engine, which enables the machine to track on and off standard plant trailers and between borehole locations without the need to plug it in.

However, Richard adds, ‘There has been some successful applications and we have used the rig for well drilling activities on construction sites throughout the UK, saving 1,000s of litres of diesel fuel and contributing to reductions in C02 and particulate emissions. However, all too frequently we have had to revert to traditional diesel-powered rigs because the project owner wasn’t able to supply sufficient mains electricity at the point of use’. Clearly there needs to be a cultural shift from all involved and that extends to the project owners too.

That said, according to Richard, there are additional benefits of the electrically powered drilling rig beyond simply lower emissions; ‘The machine is far quieter than its diesel equivalent and emits less heat, which contributes to the comfort of the drilling team. The operator’s also report smoother delivery of power to the drilling functions and the motor can be maintenance free.’

However, for electric rigs to be viable in the construction sector for drilling, piling and excavation, clients and contractors will have to put increasingly more consideration into bringing power onto the site as soon as they take possession. All too often the installation of sub stations and distribution can be months or years into the project; meaning that diesel plant, including generators for basic lighting and heating, are all required with the associated emissions. For a GI on a greenfield or brownfield site the problem is compounded by the insufficient or total absence of accessible mains electricity and electric rigs are unlikely to provide a comprehensive solution in the short or medium term.

Battery powered drilling rigs suitable for site investigation are in the development phase and may well offer a more flexible solution at a future point, but analogous with motor vehicles, battery life, exchange of batteries and recharging facilities are all challenges that need conquering, and the capital cost of battery rigs is also likely to be 50% more than a similar diesel-powered rig.

Why wait – act now!

Whilst the sector waits for cost-effective electric / battery powered replacements there still needs addressing the harmful emissions from diesel engines, which includes nitrogen oxides and soot particulates that are known to be extremely harmful to human health.

A first step would be for the sector to lower its emissions by operating the most up to date diesel engines, which will drastically reduce the harmful emissions. An example is shown here:

Engine Stage NOx (Nitrogen Oxides) g/kwh PM (Particle Mass) g/kwh
Stage 3a 4 0.3
Stage 5 0.4 0.015

A stage 5 diesel engine is not mandatory inside London until 2030 although Non-Road Mobile Machinery (NRMM) manufacturers, including drilling rigs, have a requirement to only supply Stage 5 compliant engines since 2020, but they have offered it as a cost option for years. It is worth noting that older style cable percussion rigs can be retro fitted with Stage 5 compliant engines, although this option is not available to all rotary rigs due to the difficulty of the mounting the exhaust gas cleaners.

Although the NRMM Low Emission Zone only applies to machines on construction/demolition sites with rated power outputs between 37-560kW, and not to all sites, the principle of best practice should apply to all sites and all categories of NRMM. Construction sites are required to maintain a register of diesel engines, but presently GI is currently not in the scope of the Greater London Authority NRMM register.

Do or be told to do!

It is incumbent on us all to do as much as we can to reduce emissions and acting early can reduce or spread any outlay or investment towards compliance. The BDA supports a more rapid move towards low carbon and cleaner emissions, but recognises that the requirement for investment to bring the UK land drilling fleet up to Stage V.

However, clients and designers of ground investigation and drilling projects are considering including clauses in their geotechnical specifications requiring the drilling contractor to demonstrate how they are reducing their harmful emissions and not only in Central London or other cities with Low Emission Zones. Being able to demonstrate that you are pro-actively reducing emissions not only improves the air for everyone but could have a positive bottom-line impact too.

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