‘Anaerobic Digester’ or ‘AD’ refers to the natural process of using bacteria to break down organic waste (animal or food). This process happens naturally in a sealed and heated oxygen-free tank called an Anaerobic Digester, which then produces Biogas (for energy and heating) and Biofertiliser (Digestate).

‘Anaerobic Digesters’ are also called ‘Biodigesters’ to maintain a reference to the ‘biological’ digestion process, just with fewer words.

Anaerobic Digesters are used to break down and recycle organic matter. Anything that is biodegradable can go into a Digester and is called ‘Feedstock.’ Anaerobic Digesters manage feedstocks from farms, cities, organisations etc – wastes that otherwise would not have a purpose.

Several times throughout the day a fixed amount of effluent, or effluent with organic industrial wastes or food wastes in it, is pumped into a reactor (Anaerobic Digester tank).  The insulated tank is heated and stirred over a 21–25-day cycle, where the structure of the effluent is modified into a potent organic biofertiliser called Digestate.  Through the Mesophilic Digestion process inside the reactor, methane-rich biogas is captured, cleaned (H2S removed), dried, and burnt via internal combustion engines attached to a generator (CHP unit), converting the Biogas into significant volumes of valuable heat and energy, i.e. electricity and hot water.

Anaerobic Digesters consume waste products and ultimately turn them into energy (Biofuel) and organic fertiliser (Biofertiliser). They avoid greenhouse gas emissions from decaying organic matter by instead harnessing and generating renewable electricity, heating buildings, and/or fuel transport in some cases. Digesting helps to manage nutrients and keep them in productive cycles, instead of polluting waterways. The Biofertiliser from the Digestate supports soil health, reduces farmers’ expenses, and improves crop yields. Healthier soil means better water retention, less irrigation, and reduced soil erosion and nutrient runoff (leeching).

Farmers we have spoken to have all said that using Digestate on their farm, instead of mineral or synthetic fertilisers, brought “life” back to their farms. Worms, insects, birds, etc.

On-farm Anaerobic Digestion is hugely popular and effective throughout Europe and the Americas, with thousands in successful and profitable operations. Unfortunately, there have been few incentives or reliable information for New Zealand farmers to harness this proven technology. Nor has its reputation been helped by some dangerously misinformed opportunists who have invested in poorly designed projects, doomed to fail, and all with the wrong end goal in mind. Provarko has remedied this by partnering with a tried and tested second-generation American Energy company with over 46 years of experience – Martin Energy.

Direct results are:

• Provarko Anaerobic Digesters have three end products: Biogas, a nutrient-rich liquid called Digestate, and a solid by-product similar to compost.

Indirect results are:

• Provarko Anaerobic Digesters provide farmers with higher returns from their farm investment
• Provarko Anaerobic Digesters bring life back to your farm
• Provarko Anaerobic Digesters support a cleaner environment
• Provarko Anaerobic Digesters lower carbon emissions

YES, they do this in two ways:

1. Undigested manure and food scraps are responsible for greenhouse gas emissions on agricultural operations and landfills.  Anaerobic Digestion reduces these emissions by processing the feedstocks (organic matter) into usable products, that are also environmentally friendly.
2. Secondly, Anaerobic Digesters capture methane, clean it, then generate Biofuel, which is then turned into electricity and heating. Therefore, proving a positive alternative to fossil fuels, and offsetting the use of coal or natural gas. Due to the technology’s prevention of emissions and displacement of fossil fuel energy sources, some even call Anaerobic Digestion ‘carbon-negative technology.

Burning Bio-methane does create Carbon dioxide; however, CO2 is 21 better than Methane and 310 times better than Nitrous oxide that would otherwise be released into the environment.

About 20% of the hot water generated is used to heat the Anaerobic Digester tank. What electricity is not used on the farm, can be sent to the grid.

Biogas is produced when bacteria (Methanogens) decompose organic matter in the absence of oxygen. Methane is a flammable gas and can be converted into electricity, heat, and even transportation fuel.

This depends on your farm’s needs, set up, and what other “feedstocks” (fuels) are available.  However, an example could be – if you can collect 100% of the effluent from a herd or 500, this would generate approximately 83kwh of power and approximately 100kwh of hot water.  This usually ample to run a farm of that size with excess generation being sold back to the grid.

Provarko Anaerobic Digestion plants can take any organic matter, known as ‘Feedstock’. Each feedstock has its own biogas potential, and some materials generate more biogas than others. Generally, however, a feedstock that is high in sugars and oils will produce more biogas.

Yes, absolutely, and Provarko provides this shared solution with the use of a tractor and tanker, or pumping systems between neighbouring farms.  Advantages are:

1. Multiple farms can utilise environmentally superior and natural organic manure
2. We build a digester system big enough to produce electricity in a microgrid to feed several farms
3. Different farms that milk at different times will ensure the year-round operation of the digester
4. Once the Digestate is taken back to the original farm it can be applied directly to the field
5. There is a larger pool of money available to ensure an effective operation
6. Providing farms will no longer require mineral or synthetic fertilisers

Anaerobic Digester systems are an investment into the sustainable future of your farm and the wellbeing of New Zealand waterways.  Whilst there is no ‘one price fits all’ offering, as all designs are custom-built to specifically fit within your farm and operation needs.  The good news is Provarko Digesters can be modular, meaning we can build an affordable system in stages if required, which can be added to without extensive re-engineering.  We believe, with small adjustments to farming techniques, our units would have a 4-year payback.  Faster if the hosting farm can utilise all the electricity and the huge amounts of hot water the plant produces.

The engine itself requires a rebuild at approximately 70,000 hours, and this cost we have built into the 4-year payback cycle.  The rest of the system will last many decades, with correct care and maintenance.

Digesters can be large or small– they range from ‘Micro-Digesters’ used to process the organic waste from a single home to industrial scale digesters handling hundreds of tons of material at a time.  The size of the tank is relevant to the size of your farm requirements.  Provarko standard sized tank is 22 meters in Diameter.

Provarko Limited has partnered with Martin Energy Group, a tried and tested second-generation American Energy company with over 46 years of experience, which operates on a global scale. Meaning we are not “reinventing the wheel” rather when we turn the key – it will work!

Simple!  Contact raymond@provarko.co.nz or Ph: 0274 322 282 to start the process.  From here we will collect information about your current setup, size of herd or stock, ascertain your desired outcomes, arrange a site visit, and then quote accordingly from there.  This process may take several weeks as there is a lot of information to work through with our customers – however, a critical part of our Anaerobic Digestion plant design process.