Biomimicry and the Sahara Forest Project
There are a number of key biomimicry ideas that have been a source of inspiration throughout the project. The Namibian fog-basking beetle, which has evolved a way of harvesting its own fresh water in a desert, was important in developing the design of the seawater-cooled greenhouse. The characteristic of ecosystems being regenerative was a powerful driver for the team to strive for solutions that went beyond ‘sustainable’ to ‘restorative’. The latter point was taken further with an in depth comparison of conventional human-made systems and ecosystems which revealed the following contrasts:
Encouraged by recent history
The Sahara Forest Project team’s interest in restorative technologies developed further when they studied some of the world’s deserts and discovered that many of them supported vegetation in recent history. For instance, when Julius Caesar arrived in North Africa what greeted him was a wooded landscape of cedar and cypress trees. The Roman writer Pliny marvelled at the abundance of fruits in the forests and the variety of animals. Caesar’s armies set about clearing the land to establish farms and for the next 200 years North Africa supplied the Roman empire with half a million tonnes of grain a year but, over the years, deforestation, salinisation and over-exploitation of the land took its toll. Productivity dropped and the climate changed. It was a highly extractive model of land use which in many ways became the dominant paradigm for the next two millennia.
Satellite imagery of global photosynthetic activity shows how the boundaries of growth at the edges of deserts shift back and forth quite dramatically over the course of each year. This raises the question of whether interventions can be made at these edges that could halt, or even reverse, desertification. For the team on the Sahara Forest Project much of the inspiration for tackling this challenge came from studying the organisms that have already adapted to life in deserts. In addition to this, a core biomimicry principle on the scheme was to combine proven technologies and to explore the potential symbiosis between them.
The three core components of the Sahara Forest Project are saltwater-cooled greenhouses, concentrated colar power (CSP) and technologies for desert revegetation. The synergies arising from integrating the technologies into low-waste interconnected systems improve performance and economics compared to those of the individual components.
· Some of the synergies between the technologies are as follows:
CSP needs a supply of demineralised water to keep the mirrors clean and to run the turbines
The greenhouses are effectively acting as cooling towers for the CSP and get rid of the excess heat.
The CSP mirrors make it possible for a range of plants to grow in the shade underneath and, if the mirrors were placed immediately behind the greenhouse, it could extend the zone of elevated humidity behind and consequently promote more restorative growth
The new outdoor vegetation stabilizes soil and reduces dust so that more sunlight reaches the mirrors of the CSP installation.
The fog-basking beetle
The seawater-cooled greenhouses developed by the Sahara Forest Project essentially mimic and enhance the conditions in which the Namibian fog-basking beetle harvests water in a desert: evaporation of seawater is increased to create higher humidity and then a large surface area is created for condensation. Saline water is turned into fresh water just using the sun, the wind and a small amount of pumping energy.
Striving for zero waste
Evaporating large amounts of sea water to cool the greenhouses and the CSP will clearly result in quantities of salts and the team sees under-utilised resources, not as a problem but, as an opportunity to add to the system to create more value. Seawater contains almost every element of the periodic table and the aspiration is to strive for a zero waste system by extracting as many resources as possible from the brine. For instance, magnesium chloride can be extracted and this is valuable both as a drying agent in air conditioning systems (one of the lowest energy ways of cooling air is to evaporate water into it and then use a desiccant to remove the excess humidity) and for the recovery of phosphate from waste water (magnesium chloride combines with the phosphates and nitrates to form a useful fertiliser called struvite). While the commercial extraction of elements like gold are very unlikely to be viable it should be possible to extract some of the elements that have been lost from soils through intensive agriculture and return these to desert soils to assist with the regenerative aims of the project. In so doing, the project will be closing an important loop in a system of land use and nutrient management that has been to a large extent linear and wasteful since Caesar’s time.
Perhaps one of the most important distinctions shown in the list of comparisons above is that conventional human-made systems are engineered to maximise one goal whereas ecosystems have developed over time towards an optimised overall system. The team has been working to develop the idea of system optimisation as far as possible in developing a whole cluster of technologies that can be connected up so that the waste from one becomes the resource for another.
The team intend to use biomimicry throughout the design and development process. In the future it may be possible to make mirrored surfaces from proteins at ambient temperature and pressure as silver Scarabaeidae beetles do, scratch-free coatings for the mirrors based on the sand skink which can swim in sand without suffering from abrasion, linings for the sea pipe that use the same anti-fouling furanones found in seaweeds, condensation surfaces based on camel’s nostrils and many other innovations that would add to the project. Camels have highly intricate nasal structures known as turbinates which are made from spongy bone covered with richly vascular tissue. As the camel breathes in, the tissue is cooled by the evaporation of water into the dry air. During exhalation, the humid air from the lungs passes this large area of cool surface and much of the humidity condenses to allow re-absorption. The intricacy of the turbinates results in very small distances between the surfaces and the centre of the air stream which increases the potential for heat and moisture transfer. Inevitably, during the heat of the day, a certain amount of water is lost and the cooling created by this process is transferred by blood capillaries to the brain – in extreme conditions keeping this vital organ 6oC cooler than the rest of the camel’s body.
Often approaches to environmental challenges involve tackling specific problems when more could be achieved by addressing the systemic failure rather than the individual symptoms. The Sahara Forest Project shows how biomimicry can help to address a whole range of challenges including creating fresh water, shifting to the solar economy, regenerating land, sequestering carbon in soils, closing nutrient cycles and providing employment to large numbers of people.
Written by Michael Pawlyn
Michael Pawlyn is the Design Manager and a Board member of the Sahara Forest Project. He is a well-known propopent of biomimicry and wrote a book titled Biomimicry in Architecture published by RIBA Publiciations. Some of the text above is reproduced from the book with kind permission of the publisher RIBA Publications.