Carbon is one of life’s most important building blocks and every cell in your body contains the element. It would be far easier to list everything you touch or see that lacks carbon than everything that contains it.
Activated carbon (activated charcoal) is often considered one of the world’s most powerful adsorbents. It‘s utilised in a wide range of industrial and residential applications that include water and air purification, removing unwanted odours, general gas emissions and both organic and inorganic components.
Activated Carbon NZ (ACNZ) is a small New Zealand-owned company. They are the only company producing activated carbon, as all other activated carbon in NZ has been imported and made from coal or coconut shells.
The activated charcoal produced from ACNZ’s Taupō plant is used for stormwater, wastewater, potable water, effluent filtering, gas recapture and filtering, odour control, cosmetics and supplements. Recently the company has begun to investigate its use in the dairy sector and the agriculture sector in general.
ACNZ director Grant Hughes describes activated carbon as “nature’s magnet” for attracting mercury, nitrogen and sulphur. It conducts electricity to a degree, insulates heat and decolours some liquids, which has proved beneficial to the wine industry.
Activated carbon is a component of dyes, pharmaceuticals and paints. Due to its high surface area, it is sometimes used as a binder. ACNZ has a trial going with a company experimenting with using activated carbon as a binder in an organic natural building process for housing.
“A simple description is that activated carbon grabs most of your nasties. It has many uses and we seem to find new applications every day. For example, studies have indicated that adding activated carbon to a cow’s diet can result in a reduction of methane and an overall improvement of their health and wellbeing,” Hughes says.
There is some overlap between low-quality activated carbon and high-quality biochar. Biochar is formed by burning and then starving it of oxygen. ACNZ uses a pyrolysis process to bring the material up to a high temperature in the absence of oxygen, with no burning.
ACNZ is working on ways to use high-absorbance charcoal (biochar) as a carrier for biofertilisers. It can be preloaded with fungi, bacteria and other elements and applied to pasture or soil.
“There’s a growing demand for high-absorbance charcoal in our dairy industry as a way to reduce nitrogenous fertiliser use. We’re producing high-absorbance charcoal now, but not in large enough quantities for the agricultural sector. We aim to meet that demand,” he says.
“We took some porous bags full of activated carbon to a local dairy farm and placed them in their effluent pond for a time, removed them and placed the effluent soaked carbon around some tomato plants and undertook some comparisons. It was amazing to see how much it boosted the growth of those plants.
“I can see a use where activated carbon is placed into effluent to absorb the nitrogen. It could then be taken out and easily transported and spread around the farm and used on areas other than the effluent irrigation platform. It could even be taken down the road to the runoff.”
For that to happen, ACNZ must be able to produce large quantities of activated carbon and Hughes feels that they are headed towards that goal as they have the knowledge to build a plant capable of achieving those economies of scale. Their current plant is in many ways still a prototype, but it does produce industrial quantities of activated carbon.
They use organic Pinus radiata waste sawdust produced by the forestry, logging and milling industries for their product. The company’s plant location in Taupō was chosen due to its close proximity to the local forestry and milling industries.
“Pine trees have been planted throughout New Zealand and we must do something with the waste. There’s huge waste in the forestry industry where they’re not achieving 50% utilisation from plantation forestry,” he says.
“Every kilo of rotting sawdust emits 1.6kg of CO2 into the atmosphere. We can convert that waste sawdust into a high-value product. We don’t have to dig up the seabed or mine for it. There are mountains of Pinus radiata sawdust and other biomass waste in New Zealand and we need to do something with it.”
Sawmills produce hundreds of tonnes of sawdust a day and that which is not utilised inside the mills or used for stock bedding (seasonal), is usually dumped for the cost of the transport.
“New Zealand has a huge supply of biomass (sawdust) to make high-quality activated carbon, so let’s use it. It’s natural and we’re stopping CO2 from entering the atmosphere. It just makes sense,” he says.
Hughes foresees many new uses for activated carbon in the NZ market for soaking up industrial pollutants out of stormwater and wastewater.
“Activated carbon has tremendous potential for polishing up storm and wastewater. Especially after dropping the solids out of the effluent through a weeping wall or similar system that removes the suspended solids. You can really polish up the remaining water with activated carbon filtration,” he says.
“Activated carbon has huge potential for the dairy industry and we’ve already had interest in its potential from some New Zealand fertiliser and dairy feed companies. It’s sustainable, organic and requires no importation.”
