Obtanium Engineering

Modern dairy tends to involve rather complex engineering and use lots of energy. A micro dairy is not necessarily much less complicated. I am trying to creatively (re)use available materials and renewable energy to help Sellar Dairy move toward a vision of sustainable and regenerative farming.


Energy is everywhere in all imaginable forms. Our modern way of life uses lots and lots of it. Some forms of energy, like oil and coal are particularly useful to us, more so than the same amount of energy in, say, heat.

Much of the way of life we take for granted is based on massive reserves of fossil fuels. These resources have been found in such large quantities that we have been able to build a huge civilisation based on them.

Between the growing awareness of resource limits and climate change, a movement to find alternative ways to live is rapidly gathering momentum.

Food production in our modern world is at the edge of both energy and climate. Farms, on the whole, use a lot of energy and rely on stable and predictable climate.

About a century ago, more than 2000 calories of food were produced for every calorie of fossil energy used in US broad-acre agriculture. These days that is reversed!  Yes, more than 2000 calories of fossil energy are used to produce each calorie of food.

Despite the resource limits we face, the abundance of cheap and useful energy from the last century has lead to a huge amount of discarded resources. Making things from available materials, or Obtanium Engineering, is one of the best ways to make the energy, already invested(embodied energy), go further.

Obtainium Engineering Farming

To be a farmer is to be a Jack-of-all-Trades. It is not uncommon to find some ingenious use of available material on farms. Its common place on farms to maintain equipment and creatively use available materials. I am certainly not alone as a farming Obtanium engineer. It seems to me that the “quality” of Obtanium in rural and farming areas tends to be lower for at least two reasons. Firstly, these folks tend to be less wasteful in the first place and secondly tend to reuse waste more effectively.

Being closer to centres of population, wealth, industry and big business seems to “improve” the quality of Obtanium. Obviously this means more is being wasted in these areas. Our culture needs to learn to waste less. But in the mean time we need lots more Obtanium Engineers to salvage these fantastic resources.

Obtanium is not as reliable or predictable as new materials by its very nature, requiring a greater degree of flexibility, innovative design and some times some inefficiencies. For many people efficiency is one of the keys to sustainability but its really only part of the picture. Here lies the Prius problem. We need to also consider the amount of energy to make new tools, not only their operating cost. Sometimes the total energy used is less to continue to operate older equipment than replace it with newer, higher efficiency, equipment.

Reuse of materials isn’t always easy, often taking longer and potentially  sacrificing some degree of reliability or consistency. This makes redundancy and serviceability important design requirements. Obtanium engineering is a slow way. Perhaps it can be thought of a bit like Slow Food.

For the last year I have been sourcing materials, designing and construction the various components of Sellar Dairy.

I have discovered that the more technically demanding the system being designed, the more challenging it is to reuse materials as its particularly difficult to know the exact specifications and capabilities of second hand equipment in order to do the necessary calculations to ensure the components of the system will function correctly together. For this reason, industry tends to be incredibly wasteful, throwing away(recycling) huge amounts of perfectly functional equipment. A functioning machine that is melted down for scrap is a huge waste of all the energy it took to make it compared to reusing it.

Our Design, Engineering & Reuse

This is a somewhat flexible process that adapts to the available materials as they are sourced. Below are a few snap shots of the evolving designs for some of elements of Sellar Dairy and examples of the wins, losses and challenges in reuse.

The Factory

We had done some initial designs sufficient to decide on a 40′ insulated shipping container as the base for the moveable Sellar Dairy factory.

The container
The basic plan for the factory to be built into the container.
Making a start
Putting a floor in and dealing with the irregularities of used materials

The floor of the container wasn’t all even as it had suffered some damage from years of use carrying heavy cargo. To accomodate for the damaged to the floor in one corner I had to create tapered supports to carry the ply flooring substrate.

Reusing refrigeration panel for the coolroom walls.

The Vat

The heart of the dairy is the pasteurisation vat, both in an engineering and energy use sense. Tess had a relatively good idea what she needed in size and found a good candidate early on.

200L Pasteurisation Vat. An ex-yogurt culture test vat that had been cut down is size.

The energy required for the vat to heat, for pasteurisation, and cool, for storage, is significant. The systems required to do this heating and cooling are complex.

Heating and Cooling Design

Basic overview diagram of heating and cool – v2.2


Electricity is a very high grade energy. Its able to do almost everything we need, including make heat. But its a huge waste to degrade electricity to heat. Heat is one of the most abundant forms of energy around us and its much harder to turn it into electricity than visa versa. Solar thermal is much more efficient and lower tech than solar photovoltaic for creating heat. We will use solar thermal panels to provide much of our heat needs through the hotter months.

Used solar thermal (solar hot water) panels.

I have refurbished damaged panels destined to be scrapped.

Rewelding cracked (from frost damaged) panels


Refrigeration and cooling systems are one of the biggest contributors to climate change(see Drawdown). I have been particularly keen to ensure our impacts from our cooling needs are as low as possible. We are recovering many parts from the large old, leaking and failing refrigeration system from the two refrigerated containers we have. We(HOFC) got a second one as part of the infrastructure for the hub(our co-op shared facilities). 

The old container refrigeration system

The 8 kg of R-134a refrigerant gas from the two refrigeration units is equivalent to about 11,440kg of CO2 in terms of its greenhouse effect on the atmosphere.

The average Australian travels a bit over 11,000km/year. In a car that uses about 7.5L/100km this would equate to about 2.41 tons of CO2 emissions(ref). So the refrigerant gas from our two containers, if released, is something like 4.7 years of driving for the average person! Eeek.

We had the refrigerant gas professionally recovered by Graeme Ellis and will use it in the system we are rebuilding. Greame has been great in working with us on this journey of reuse.

I have recovered the compressors out of the systems.

Shipping container refrigeration compressor ready for sandblasting, painting and an oil change.

Waste Heat

Almost everything  seems to make waste heat. Particularly lots of industrial processes. We are able to capture some of this waste heat. Our refrigeration compressor will produces lots of waste heat(more than 10kw). By retrofitting water cooling onto our compressor we can make it more efficient. Also we are able to run the hot water through a heat exchanger to recover(into our hot water system) some of this waste heat.

A tube-in-tube heat exchanger for waste heat recovery I just built from scrap copper piping.


The systems require lots of pumps for all that heating and cooling.

So many pumps get scrapped that just need a service. I have recovered lots of pumps from the scrap metal that just need new bearings and seals. And then there are the ones that are still perfectly functional without any servicing too. Even brand new stuff makes it into the scrap!

Pumps diverted from scrap

Cold Storage

We’ve found old 3000L milk refrigeration vats second hand to store our cold process water for chilling the milk vat.

Cold water storage tanks

These are a good illustration that reuse is not always predictable or easy. When Graeme Ellis tested the refrigeration coils, he discovered that only one of the two vats was useable. The second was leaking badly and upon closer inspection failed repairs were visible. We actually only need one. Its often necessary to get more than you are expecting to use when engineering from obtanium.

Hot Storage

hot water cylinders arriving

The design for the hot water storage has been adapted around these 4 415L hot water cylinders from our own local second hand materials business, the Salvage Yard. A fantastic business that support these values of reuse. 

Perhaps we can think of Obtanium Engineering as an effort to improve embodied energy efficiency. Really just getting the most out of what we already have.

This post has primarily focused on reusing energy already stored in stuff(embodied energy). The other side of the coin is also the dynamic energy that we use to run the systems. In a future chapter I will go into more detail about the energy usage and production side of the dairy.

I would like to end with a sneak peak into an exciting and innovative renewable energy system we are looking to demonstrate. Like most things innovative, nothing is certain but the system is showing great promise.

Inovation in renewable energy – Inresol micro CHP(combined heat and power) generation unit.

Thanks for your support and interest in Sellar Dairy.

Oliver Holmgren

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