2025 Annual Inkwell Carbon Update
Each year we calculate our carbon sequestration and emissions at Inkwell and share that information for those curious about regenerative viticulture.
In 2019, we chose to practice regenerative viticulture at Inkwell because we realised that our only chance of adapting our vineyard to be resilient to the extreme weather events of a changing climate involved increasing the amount of carbon in our vineyard.
Despite our prior investment of 17 years of sustainable and organic farming of these soils, we came to this conclusion after measuring bare undervine and midrow soils at 65 degrees on a 44-degree day – hot enough to kill single cell life.
Soil carbon is our core metric because:
- it holds 4-5 times its weight in water enabling additional water retention. For example, a small .25% increase in SOC equals about 3.5 tonnes of additional carbon per hectare and an increased water holding capacity of about 16,000 litres per hectare. At 2000 vines to the hectare, this is an additional “bank” of 8 litres of water available per vine on a hot day. This soil moisture can be the difference between grape production or crop losses during extreme heat events.
- helps bind soil together to improve water ingress during rain and irrigation while deterring erosion and soil loss
- works with nitrogen or other minerals in a cycle to encourage diverse soil life and availability of nutrients to the plants
More carbon rich soil enables us to mostly keep the soil covered with living plants year-round which lowers vine stress due to heat events with cooler and moister soil than bare dirt.
While we didn’t start intensive soil testing until 2022, we now know that in the first 19 years of sustainable and organic farming at Inkwell (2003 to 2022) we sequestered about 140 tonnes of carbon in our soil (SOC) across 10.6 hectares or, about 13.2 tonnes per hectare or, about 700 kilograms per hectare per year on average. At a square metre level, that’s just an increase of 700 grams of carbon. In terms of SOC, this was an increase of about .05% per year on average. While that seems like a really small amount, it exceeds the carbon we’ve emitted making, bottling and distributing wine at Inkwell since 2005. Considering we weren’t really trying to accomplish this outcome most of that time, it’s a pretty cool result.
In 2022, we started intensive soil testing by sampling each of our 10 distinct vineyard blocks on a rolling three-year basis, while we sample two control blocks annually. This gives us an idea of how we’re doing both season to season and over time as sequestration is a long-term process with a lot of ups and downs to be expected on the journey. We sample at the same time using the same method each year in August to try and keep things as scientific as possible. We then track those results in a spreadsheet that allows us to measure the long-term compounding rate of carbon at Inkwell.
The only different practice we employed over this period was switching to a USA based laboratory in 2025 because they have more current testing methods and capability. The test we use, the Haney Test, is the first new soil test in decades approved by the USDA. It is available at only one lab in Australia at this point and very expensive. Including the cost of air freight, the cost of our samples being tested there is about 60% of the price of the Australian lab and very competitive with older tests in Australia price-wise.
While our results from 2022 and 2023 were encouraging, 2024 was the driest on record in South Australia. Drought is not ideal for building soil carbon as microbes need soil moisture to thrive. So, it was with a great deal of interest that we sent our results off to the laboratory. Because we do not sample every block every year (it’s too expensive to do all of them each year), we can quantify sequestration in measured blocks in years one and two of our cycle and conservatively estimate totals in year 3. 2025 was the end of our first three-year cycle.
According to the lab results, our calculations showed the total soil carbon added in our vineyard between 2022 and 2025 equalled 114 tonnes or 10.75 Tonnes per Ha. This is an average increase in SOC of .76% over that three-year period or, roughly, .25% per year. This is an average of about 3.6 tonnes per year per hectare of carbon sequestration compared to our previous (2003-2022) average rate of .05% SOC per year. The 2022-2025 results are a 517% increase in the rate of sequestration over the prior 19 years. This change is entirely a result of regenerative farming practices.
The practical question is, at what cost? The total costs of managing our regenerative organic system are less than prior approaches because: our plant health has improved to the point that we have only needed to spray sulfur and / or copper a total of five times over the last four seasons (the local average is 5-8 foliar sprays per season), we have not applied NPK fertilisers, mulch or compost since 2019 and we have not sprayed any herbicides. We apply micronutrients with our existing foliar sprays and undervine knifing / mowing costs are the same as in the past.
On the increasing cost side, we now slash and crimper roll midrows once more per year each than in the past. In years with less than two foliar sprays, we need to add a foliar spray or two to apply micronutrients and biological amendments that we think helpful. We seed diverse cover crops (legumes, cereals, brassicas, etc) in autumn with untreated seed that costs about $140 per hectare plus the cost of seeding. In addition, we apply aerated compost teas using our ground / broadcast spray unit five or six times per year to encourage soil and plant health. The teas are inexpensive (less than $10 per hectare) to make and work well for us but are not necessary to practice regenerative viticulture.
The result for us is lower overall operating costs, equal or greater fruit yields at very high quality but a bit more work because of the mix of work that we do ourselves now vs contracting out.
The carbon emissions equation – we calculate our Scope 2 carbon emissions (which includes growing, production, packaging and distribution emissions) using a slightly modified formula created by the AWRI*. Using this we calculated that our emissions were 6.95 tonnes in 2025, 8.5 tonnes in 2024 and 5.84 tonnes in 2023. The biggest variable in these numbers is the amount of fruit harvested and made to wine.
Over three-year period, the results are:
Carbon sequestered in our vineyard – 114 tonnes
Carbon emitted making, packaging and distributing wine – 21.3 tonnes
Net carbon sequestered – 92.3 tonnes or about 30 tonnes per year
This means we are sequestering 5.3 times as much carbon as we are emitting in the wine growing, wine making and wine selling business at Inkwell currently. We realise that soil carbon won’t increase this rapidly forever but, reaching levels of at least 2.5% SOC in all of our blocks is our immediate goal.
Two final numbers: from 2003 – 2025 we have increased SOC at an average rate of a bit over 8% per year on a compounding basis equalling 254 tonnes of SOC. This equals about 24 tonnes of carbon per hectare and additional water holding capacity of over 100,00 litres per hectare. These results are literally “bankable” and growing every year.
Note: These emissions figures do not take in our micro-hotel, home or personal lives however, our personal foot print is relatively modest as we only use renewable electricity in our home, have an electric car, do little air travel, etc. and only use LPG as a backup for renewable hot water in our hotel. They also do not include the thousands of native trees and bushes or other environmentally friendly things we’ve done on the rest of our property.
* The modifications we made to the AWRI carbon calculation were to account for our already carbon aware practices such as using only renewably produced electricity, zero NPK fertiliser usage, no wine chilling in the winery, etc.
Finally, to clear up any confusion between carbon and CO2, we refer only to carbon to keep our analysis “apples for apples”. CO2 is 3.67 times as heavy as carbon due to the weight of the oxygen molecules. So it is equally true to say that we sequestered one tonne of carbon as it is to say we sequestered 3.67 tonnes of atmospheric CO2 for those of you wanting to know CO2 figures.