New Zealand's biomass resources

Once upon a time, we used to call the byproducts of primary industry rubbish – like pulp from juice factories, prunings from grape vines or slash (harvest residues) from forestry. Now these waste streams are seen as valuable resources and are grouped with other biomass streams – they’re called residue biomass. Biomass streams offer exciting opportunities to convert renewable resources and what was once considered waste into useful new materials or fuel alternatives.

The drive to convert biomass is part of a global drive to find solutions to a number of wicked problems such as:

• climate change caused by the burning of non-renewable fossil fuels for transport and to power industry among other things
• single use plastics and plastic pollution caused by many plastic types being non-biodegradable.

What is biomass?

We use the term ‘biomass’ to describe living or recently dead biological material. Biomass contains stored energy produced from the Sun. Plants absorb the Sun’s energy through a process called photosynthesis. When we burn biomass, for example, wood in an oven, the chemical potential energy that was stored is transformed into heat energy.

Burning wood is not the only way to release energy, and wood is not the only type of biomass available. Typically, the term biomass is used to refer to plant material but it can also include animal matter or biodegradable wastes. Organic material that has been transformed through geological processes, as is the case for fossil fuels, is not included in this description.

Different biomass streams also present different chemical structures and components that can be utilised in the drive for biodegradable and compostable materials and bioplastics that can replace more problematic plastic types, such as those that cannot be recycled.

New Zealand has a strong primary industry focus. This means that we also have many biomass streams available. In New Zealand, the biomass resources can include woody resources (including leafy plants), agricultural plant resources, residue from agriculture and forestry, as well as municipal (civic waste from towns and cities) and industrial wastes (this includes liquid sewage and manure).

New materials from biomass

In New Zealand, there is a lot of research looking at ways to utilise biomass from waste streams. The results of some of this research are already in production, such as the Zespri biospife – a compostable tool for eating kiwifruit made from kiwifruit residues – created by Scion and Zespri. Another product developed by Scion is the grape vine net clip – made from marc – the left over grape skins and seeds from the juicing process.

Potatopak (now rebranded as Earthpac) makes and sells potato plates. The biodegradable plates are made from potato starch – a waste product from chip-making.

Biofuels

Biofuels are fuels that can be produced from or made up of a renewable material. Biomass streams that could be utilised for biofuel production are municipal solid waste (rubbish that often goes to landfills), waste wood from construction and demolition, harvest residues left in forests and co-products from existing biomass processing such as chips from sawmills or tallow from meat processing.

Biofuels can be part of a suite of solutions to reduce the current dependence of New Zealand on fossil fuels for transportation. The use of fossil fuels for transport is a significant percentage of New Zealand’s greenhouse gas emissions that are contributing to climate change. Road transport made up 43% of New Zealand’s carbon dioxide emissions in 2018 – emissions from this source increased by 22% between 2009 and 2018.

Right now, liquid biofuel use in New Zealand is less than 0.1% of total liquid fuel sales. Fonterra’s Anchor Ethanol plant is producing bioethanol from whey – a byproduct of cheese. This is blended with petrol and sold at retail outlets. There is also work being carried out to produce biodiesel from tallow (animal fats) and other biomass streams.

Some of the biggest hurdles for the development and use of biofuels here is the high cost of setting up to produce the biofuel and other value-chain issues. Growing a crop specifically for biofuel may also result in land being taken away from food production – something New Zealanders may not support.

The use of biomass from waste streams has a number additional hurdles including:

• available volumes of biomass are low compared to fuel demand
• tallow and sawmill chips already have existing end uses and established values outside of biofuel use
• it might not be technically or economically feasible to collect biomass that may be dispersed throughout the country.

There are a number of technologies that are used to convert energy from biomass material into fuel we can use. Not all of the technologies available have been used to produce biofuel or tested to run at a commercial level in New Zealand.

Conversion technologies for biofuels

Here are examples of conversion technologies and how useful they might be to generate fuel from biomass:

Combustion – the burning of biomass to generate heat (for example, wood). The energy product generated is either heat or heat and electricity. Combustion technology is used to heat water. The resulting steam can drive an electricity generator, and the heat that is produced can still be used. This technology is commonly used in New Zealand.

Gasification – using partial combustion to produce gas from biomass. Usually, the types of gases that are being produced are carbon monoxide (CO), carbon dioxide (CO₂), hydrogen (H) and methane (CH₄), which can then be used in internal combustion engines. This technology is not yet fully commercial in New Zealand.

Pyrolysis – using heat in the absence of oxygen to break down organic matter to its chemical components. The energy product using this technology is typically bio-oil. To produce a bio-oil, moderate temperatures are needed. The original biomass material needs to be dry for this process. There are no commercial pyrolysis systems in New Zealand working on fuel, but there are a number of commercial operations and enthusiasts around the country using pyrolysis to make biochar – carbon specifically burnt to add to soil – in order to reverse climate change through carbon sequestration and provide valuable soil conditioners. A number of these groups are members of the Biochar Network New Zealand. A news video and further information can be found here.

Anaerobic digestion – naturally degrading organic material in the absence of oxygen that produces biogas. This technology is typically used to treat wastewater sludge and organic waste. Anaerobic treatment has been applied to a wide variety of solid and liquid organic wastes, including waste from food and beverage production (sugar, soft drink, potato, vegetable, distillery and brewery wastes); meat, dairy and wool processing; and pharmaceutical and chemical industries. The significant advantages of anaerobic processes are low energy use and reduced sludge production, generation of biogas and the ability to extract valuable fertilisers from the digested residue. This technology is well established in New Zealand.

Chemical and mechanical processing – converting canola, waste oil and tallow from meat processing to biodiesel by pressing and or transesterification. This technology is used in New Zealand to produce biodiesel in relatively small quantities from waste cooking oil. It is most likely that canola crops may be used for the production of oil for biodiesel.

Biochemical and enzyme technology – this technology involves biological catalysts that can be used at critical stages of the bioconversion process to replace more energy-intensive methods. Ethanol is being produced from biochemical conversions of sugars and starch, for example. The ethanol is usually blended with the petroleum fuels, but they can also be used on their own. Using bioethanol or biodiesel means we don't burn quite as much fossil fuel. Bioethanol and biodiesel are usually more expensive than the fossil fuels that they replace, but they are also cleaner burning fuels, producing fewer air pollutants. This technology is still being researched in New Zealand.