Award-winning Two Dam Sustainable project set for growth

Over the Langeberg mountains and far away, a dilapidated farm has been transformed into a thriving off-grid Net Zero Carbon certified trout farm and self-catering accommodation. Soon, three new off-grid natural buildings will be added to the existing accommodation available to visitors.

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About four years ago, Vivian and Marco Harms, who were working near the Kruger National Park as a conservationist and a lodge manager, made the decision to relocate to the Western Cape and start their own business – Two Dam Sustainable.

Environmental care runs deep in the family, and Marco’s brother André, who started sustainability consultancy Ecolution some eight years ago, was fully on board with the project. A mission to create the most sustainable family farm and aquaculture operation began.

“Sound design should always prevail,” says André, who explains that the thinking from the start was to ensure that the operation had as low an impact as possible.

The existing structures were renovated and retrofitted using green building principles and utmost efficiency. This also makes separating the additional ‘sustainability costs’ difficult because in fact sustainable choices guided every decision.

Rather than spending capital on extending an Eskom connection to the farm, a decision to rely on renewable power was made. The farm features a novel hybrid solar and hydro solution that has most recently scooped the South African Energy Efficiency (SAEE) Confederation’s 2018 Energy Award for Innovative Project of the Year.

“Most buildings were existing already, we renovated them, slightly extended some and added the processing building as part of the shade-net covered fish farm. All electrical reticulation plus electrical and lighting fittings had to be added as there was no electrical supply other than a few panels and batteries that charged cell phones and a torch,” explains André.

The cost of all the sustainability efforts (solar and hydro power; battery bank; necessary infrastructure and equipment; energy efficient system on the fish farm etc.) are in excess of R2-million. “Although in our instance the funding came from within the family, where the values of sustainability are deeply rooted, it still requires a genuine conviction and commitment. Any ‘additional sustainability costs’ must be seen as an investment in the future of the project, the participants thereof and its environment as a whole,” says father Uwe Harms, who also plays a continued large role in the project.

“This way of thinking is diametrically opposed to the ‘normal’ understanding of the economic principle of striving for a short-term return on investment,” he emphasises.

The trout farm has on average about 4000 fish in the system. There are 300 pecan trees that are watered and fertilised with the ‘waste’ water from the trout farm. Then there is also an oat field to feed the small flock of sheep.

Two Dam Sustainable is one of only six Net Zero projects in South Africa certified by the Green Building Council SA, and it is the only project in the country that has achieved the measured Net Zero rating. This means that going beyond the design, the operational emissions have actually been calculated and carbon neutrality achieved. In October 2018, this fact led to the project scooping the Net Zero Innovative Project Award at the GBCSA’s Green Leadership Awards. It is also one of only two non-commercial certified projects, which also shows that the pricing of the Net Zero ratings, particularly at pilot stage, is more accessible to smaller projects.

The only building-associated emissions at Two Dam are from the LPG generator, and the relatively small gas requirement for cooking and water heating if solar thermal does not suffice during cloudy days. These are offset through the purchase of verified carbon credits. The project supports the Kariba REDD+ reforestation project and the purchase of these credits was facilitated through a broker (Impact Choice) who ensures that the transaction is legitimate and that the carbon credits are retired from circulation once purchased.

As an electro-mechanical engineer with his own company focused on sustainability, the project presented a fantastic opportunity for André to experiment and shoot for the sustainability stars. Valuable lessons were learned and relevant experience was gained with equipment and concepts that are replicable at scale, for application in larger commercial projects.

Sustainable stay

The self-catering accommodation portion of the farm is doing so well that a further three new off-grid natural buildings will be added to the farm to provide additional accommodation for visitors.

Again, this will be a family project. Much investigation on sustainable materials was done, and the decision was made to go with cob bricks. The required approvals are in process and the farm will now start gearing up to make the bricks, which will be a mixture of clay, sand and straw. Once sufficient bricks have been made, the building process will start. Marco attended a natural building course hosted by the Natural Building Collective’s  Peter McIntosh.

Vivian says that besides offering a tranquil, secluded getaway in a beautiful 100-year old stone cottage, the carbon neutral status of the accommodation has definitely been a drawcard for many visitors.

“I have had a few guests mention that it [sustainability and carbon neutrality] was one of the reasons they chose our cottage. We also have a lot of reading material in our information brochure in the cottage and on the website, and we try and also talk to people about what we do and how we do it,” adds Vivian.

“My favourite part about living here is being able to make more environmentally conscious decisions about our everyday life and giving my kids the opportunity to grow up in these surroundings and teaching them these valuable life lessons,” she concludes.

The ongoing work and innovation on the farm shows that it’s an evolving journey to becoming too damn sustainable.

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  • 31kWp solar photovoltaic array.
  • Solar water geysers.


  • 1kWp high pressure low volume pelton wheel turbine. (although not currently operating at full capacity because of drought)


  • 10kW LPG generator for extended cloudy days, to supply the shortfall of power demand and charge the batteries simultaneously.

 Energy storage:

  • 72 batteries with a capacity of 172.8 kWh of which only 50% should be depleted. Charged by solar, hydro and gas if necessary.

Energy efficiency:

  • Only energy efficient appliances, no hairdryers.
  • 100% LED lighting.
  • Remote sensor switches reduce need for copper cabling.
  • Naturally ventilated buildings.
  • Cool roof paint used.
  • Low head recirculating pump systems used for aquaculture.


  • Extensive alien invasive species clearing programme continues and has made a significant impact on water supply.
  • Waterless urinal.
  • A centrifugal filter was installed and a new pipeline laid for 1.2 kilometres to supply the farm – through its self-cleaning centrifugal action, this allows about 10% of its water to continue downstream, allowing indigenous riparian vegetation along the stream to remain intact, thereby controlling erosion and subsequent loss of valuable soil.


  • Alien clearing project supplies the farm with sustainable building material and firewood.
  • All toiletries and cleaning products procured are eco-friendly and/or biodegradable.
  • The majority of packaging (for the fish) is made from recycled plastic and is 100% recyclable.


  • The waste in the fish farm water is cleansed by two 10 000l bio-filters.
  • No pesticides or chemical fertilizers used – plants enriched with animal manure and worm tea from small worm farm and compost heap.
  • Recyclables are separated, collected and taken to Montagu waste and recycling facility.
  • Non-recyclable plastic waste is ‘ecobricked’ and these will be used in select parts of the new cottages
  • Fish farm features a dry composting toilet.

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