Quarry sustainability improvement is a hot topic these days and one that is getting a lot of attention from different quarters, but what does it mean in practice? Eltirus founder Steve Franklin writes.
If we want to improve the sustainability of our quarry operations, there are a number of approaches that we can take. The ultimate goal is decarbonation of the industry, which may be achieved through the use of equipment powered by electricity or perhaps hydrogen. But frankly, this is a big step and one that is going to take quite some work to achieve. This said, there is a lot we can do to improve the sustainability of quarry operations before we reach that point.
Given every litre of diesel that is burned releases 2.68 kilograms of carbon-dioxide (CO2), it stands to reason that doing everything we can to reduce fuel burn not only improves sustainability outcomes but also reduces fuel and maintenance bills.
So how can we do this?
- Use the most fuel-efficient diesel machines possible.
- Use diesel equipment effectively.
- Adopt electric or hydrogen equipment.
Use the most fuel-efficient diesel machines possible
The fuel efficiency of modern diesel equipment is substantially higher than it was in the past. For example, if we refer to Caterpillar Performance Handbook #27 and compare the fuel burn of a 775D and the current 775G in Caterpillar Performance Handbook #49 (approx. 22 years later), we see that the medium duty cycle fuel consumption has dropped from 50 litres per hour (l/hr) to 32 l/hr (and the truck is substantially more productive). This is a huge change.
If – for easy maths – we use a 2000 hours per year operating time, we see that upgrading to a modern truck fleet would save us 36,000 litres of diesel, or approximately $65,000 (assuming diesel cost of $1.75 per litre and 96 tonnes of CO2 emissions per truck per year. By the time you add up similar savings across the drill, load and haul and sales loader fleet, the savings can add up to substantial sums of money.
As mentioned earlier, not only are there fuel savings, but there are also substantial maintenance cost savings that accrue from current generation equipment, not to mention significant improvements in operator safety/comfort and environmental performance as well.
Use diesel equipment effectively
There are factors that drive up the cost of using diesel powered (or any) equipment – these include:
- Excessive idling
- Low duty cycle usage
- Incorrect fleet matching
- Excessive handling of material through poor planning
- “Busy work”
Let’s look at these one by one to get a sense of what we can do to improve performance in each area.
Excessive idling
What do I mean by excessive idling and how can we identify it? Idle time beyond 20 per cent is likely excessive. In a Caterpillar document called “How much is idle time costing you?” the author noted, “Some industry experts say that it’s not unusual for idle time to represent 40-50 per cent of total running time.” Do you have a way of measuring idle time across your fleet? Do you use it to drive change?
One cost effective method that can be used to identify idle time loss is the Propeller Dirtmate system, which provides a simple way to track when your equipment is working and when it isn’t.
Regardless of how you identify it, excessive idling does occur (machine left running on the go-line, idling through breaks to run the heater or air conditioning, etc.) and the correct identification and minimisation of it will improve your sustainability outcomes and reduce costs.
Low duty cycle usage
The duty cycle is a measure of how hard a machine is working based on the fuel consumption. As you can imagine, this can vary depending upon the application – think a haul truck running on a flat haulroad versus one hauling out of a deep pit.
But it can also tell us a lot about how effectively the machine is being utilised. If we go back to the Caterpillar Performance Handbook #49 and look up a 390F excavator, we see that the fuel burn can vary from 21 l/hr to 61 l/hr. If you keep accurate fuel records and you see this type of machine regularly using say 22 l/hr, you can tell that it is likely not working hard and is spending most of its time idling. Likewise, if it is recording 80 l/hr on a consistent basis, you probably know the fuel allocations are wrong or perhaps you are “losing” diesel.
Either way, checking actual fuel burn against manufacture duty cycle estimates can tell you a lot about how effectively your equipment is being used.
Incorrect fleet matching
Two things tend to occur in relation to fleet matching – the first is that machines are getting bigger and unless the downstream capacity increases too, they mismatch.
You can be sure that a site will always want a bigger machine than the one they have. Not only do current generation machines have significantly better fuel efficiency, but they have also grown in size.
By way of example, a 988B (1987) weighed 43 tonnes and had a bucket capacity of 5.4 cubic metres (m3). A 988K XE (2022) weighs 53 tonnes and has a bucket capacity of say 6.9 m3 – clearly a much larger (and more capable) machine.
Secondly, quarries tend to run much larger loading tools at the face than are needed, often resulting in poor utilisation. This is particularly the case where wheel loaders are used.
To reduce manning numbers, larger trucks are used, and this drives the need for larger loading tools to be able to reach over the side of the truck and load them.
Where possible, take the time to match your fleet to the job. The equipment dealers are generally very good at being able to conduct studies on fleet composition and matching – take their advice. By way of one example, a site I worked with many years ago was able to move from a WA900-3 down to a 990K wheel loader with no loss of productivity and substantial savings.
Excessive handling of material through poor planning
It’s easy to observe excessive double handling of material, particularly around the plant. Once identified, it can often be reduced through changes in fixed plant configuration including bins, extra conveyors, etc.
Where we see the biggest wins are in an area that is much less obvious: quarry extraction planning.
Our experience is that quarry extraction is rarely optimised or scheduled. Through a good understanding of the site geology, market and costs, you can optimise the deposit to maximise net present value (NPV) by extracting only material that is truly valuable and in the correct sequence. Both failing to strip early enough, or too early, you destroy value and increase equipment use and emissions.
I can’t stress how important it is to have a clear idea of your deposit and a plan to extract it effectively.
For anything other than the simplest of operations, optimisation and scheduling are not luxuries, they are vital to shareholder value and take increasing care of the environment.
“Busy work”
Early in my career, I spent time as a machine operator. The company I worked for fitted all their machines with what was known as a “Kienzle clock”, which recorded when the machine was moving and when it was not. Each week, our supervisor would show us the card and identify whether we were meeting his expectations. These were not always happy conversations.
The concept was good – they wanted to ensure that we were working without supervision, though you might also guess that given we were given a lot of trouble about being idle, “busy work” could occur to fiddle the result.
The point I am making is that you can do a lot of record keeping and analysis and pushing of the team to achieve your target metrics, but unless the results are towards a positive end, it can be perceived as more a PR exercise than of value – keep it real.
Adopt electric or hydrogen equipment
Ultimately, we will see electric, and hydrogen powered equipment (and most likely other technologies not yet envisaged). Good examples of this are the Volvo TA15 electric truck and more recently the Cat battery powered 793 (though it’s a little too big for your average quarry.) This said, we have quite a way to go to achieve this change.
Even if electric trucks are available, the installation of the power infrastructure required to charge them – not to mention the local storage needed to smooth out the charging cycle – will be substantial.
Hydrogen powered equipment will face similar challenges until the infrastructure exists for it to be safe and viable.
This might look challenging, but if we cast our attention back even one hundred years ago, you would see that obtaining petrol and diesel was nowhere near as simple or straightforward as it is now. Demand will drive infrastructure and cost reduction.
Summary
The road to decarbonisation in the quarry industry will likely not be short, if for no other reason than companies will tend to adopt new technologies only once proven and in line with fleet replacement strategies. The important thing is to start planning for it.
In the meantime, maximise the potential of the equipment you use now and do everything to use it more sustainably. A primary step to doing this will be to accurately record diesel usage per tonne of material produced and work to drive that value down through effective management of natural resources and equipment. The best part of this is that it is good for the bottom line and the environment. Let’s do it!