Ocean acidification: climate change at the sour end

A few weeks ago, I overheard a 58 year old man telling a 12 year old boy that the most dire of scientists' warnings concerning global warming over the past 30 years had failed to materialise - and that what the boy needed to learn was to be able to separate facts from propaganda.

Although it is no doubt next to impossible to be able to change such entrenched mindsets as those of this particular baby boomer, there is still extremely limited public understanding of the insidious changes currently taking place in our oceans. In addition to the rise in both sea temperature and sea level (approaching a centimetre every two-to-three years) a rapid increase in ocean acidity is now on course to profoundly disrupt marine life.

With the USA pulling out of the Paris Agreement, will the rest of world manage to pull together in order to prevent another tipping point? After all, increasing ocean acidification isn't something us non-marine scientists can directly observe. One key point that is immediately obvious is that it isn't a localised issue: as a third of atmospheric carbon dioxide is absorbed into the oceans, all the planet's seas will be affected. The decrease of 0.1pH unit in the past few centuries equates to an astonishing 26-29% increase in acidity. What's more, this change is predicted to have doubled by the end of this century. Clearly, the effect on marine life is set to be substantial.

So what is being done to assess the probable issues? Various projects around the world are using mesocosms - transparent cylinders up to ten metres long - to understand the effects of current and predicted near-future acidity levels on marine life. Coral bleaching is possibly the one condition people will have heard of (although there appear to be an astonishing number of people who think that coral is a plant rather than invertebrate animal) but sea temperature changes are as much a cause as increased acidity. Apart from causing stress to some marine organisms, leading to such conditions as lowered immune systems and so the spread of disease, acidification reduces the material available for shell and carapace formation, especially for juveniles and nauplii.

The problem isn't so much the change itself as the rate of change, which is far faster than normal geophysical processes. Indeed, one report states that over the past 20 million years, changes in oceanic acidification have been barely one percent of the current rate. Obviously, there is minimal chance of the non-directed mechanism of natural selection keeping pace with adaptations to the new conditions.

While many organisms will suffer, some such as jellyfish and toxic algae may benefit, with the latter leading to the poisoning of key fishing industry species. This in turn could lead to toxins entering the human food chain, on top of the economic issues from the decline in fish and shellfish stocks. Indeed, the US Pacific coast aquaculture industry is already experiencing a reduction in the shellfish populations. This will be in addition to the pollution of fresh waterways already explored in a post last year.

Of the various experiments aiming to understand the impact of the rapid increase, the largest project is the pan-European Biological Impacts of Ocean Acidification (BIOACID) scheme. Giant mesocosms sunk in a Swedish fjord have been sealed with local ocean water (and associated organisms) and half of them modified with the projected pH level.

Similar but small projects are underway in New Zealand and the Canary Islands, with preservation of edible stocks a key priority. Another problem with a decline in shellfish species destined for human consumption would be the loss of the raw material for chitosan, which may prove to be an ecologically-friendly replacement for plastic packaging.

Clearly, there could be numerous - and some as yet unknown - knock-on effects from the ocean acidification. Unlike the rise in atmospheric temperature, it is much more difficult to see the results of this fundamental change and for the public to understand the consequences. Yet again, the life forms affected are far from the cute poster species usually paraded to jump-start the public's environmental consciousness. Unfortunately, these may prove to be far more critical to the future of humanity and the wider world than say, giant pandas or Amur leopards. It's time for some serious sci-comm to spread the warning message!

Concrete: a material of construction & destruction - and how to fix it

How often is it that we fail to consider what is under our noses? One of the most ubiquitous of man-made artifices - at least to the 55% of us who live in urban environments - is concrete. Our high-rise cities and power stations, farmyard siloes and hydroelectric dams wouldn't exist without it. As it is, global concrete consumption has quadrupled over the past quarter century, making it second only to water in terms of humanity's most-consumed substance. Unfortunately, it is also one of most environmentally-unfriendly materials on the planet.

Apart from what you might consider to be the aesthetic crimes of the bland, cookie-cutter approach to International Modernist architecture, there is a far greater issue due to the environmental degradation caused by the concrete manufacturing process. Cement is a key component of the material, but generates around 8% of all carbon dioxide emissions worldwide. As such, there needs to be a 20% reduction over the next ten years in order to fulfil the Paris Agreement - yet there is thought there may be a 25% increase in demand for concrete during this time span, particularly from the developing world. Although lower-carbon cements are being developed, concrete production causes other environmental issues as well. In particular, sand and gravel extraction is bad for the local ecology, including catastrophic damage to the sea bed.

So are there any alternatives? Since the 1990's, television series such as Grand Designs have presented British, New Zealand and Australian-based projects for (at times) extremely sustainable houses made from materials such as shipping containers, driftwood, straw bales, even shredded newspaper. However, these are mostly the unique dream builds of entrepreneurs, visionaries and let's face it, latter-day hippies. The techniques used might be suitable for domestic architecture, but they are impractical at a larger scale.

The US firm bioMASON studied coral in order to develop an alternative to conventional bricks, which generate large amounts of greenhouse gases during the firing process. They use a biomineralisation process, which basically consists of injecting microbes into nutrient-rich water containing sand and watching the rod-shaped bacteria grow into bricks over three to five days.  It's still comparatively early days for the technology, so meanwhile, what about applying the three environmental ‘Rs' of Reduce, Reuse and Recycle to conventional concrete design and manufacturing?

1 Reduce

3D printers are starting to be used in the construction industry to fabricate building and structural components, even small footbridges. Concrete extrusion designs require less material than is required by conventional timber moulds - not to mention removing the need for the timber itself. One common technique is to build up shapes such as walls from thin, stacked, layers. The technology is time-effective too: walls can be built up at a rate of several metres per hour, which may induce companies to make the initial outlay for the printing machinery.

As an example of the low cost, a 35 square metre demonstration house was built in Austin, Texas, last year at a cost of US$10,000 - and it only took 2 days to build. This year may see an entire housing project built in the Netherlands using 3D-printed concrete. Another technique has been pioneered at Exeter University in the UK, using graphene as an additive to reduce the amount of concrete required. This greatly increases both the water resistance and strength compared to the conventional material, thus halving the material requirement.

2 Reuse

Less than a third of the material from conventionally-built brick and timber structures can be reused after demolition. The post-war construction industry has continually reduced the quality of the building material it uses, especially in the residential sector; think of pre-fabricated roof trusses, made of new growth, comparatively unseasoned timber and held together by perforated connector plates. The intended lifespan of such structures could be as little as sixty years, with some integrated components such as roofing failing much sooner.

Compare this to Roman structures such as aqueducts and the Pantheon (the latter still being the world's largest unreinforced concrete dome) which are sound after two millennia, thanks to their volcanic ash-rich material and sophisticated engineering. Surely it makes sense to use concrete to construct long-lasting structures, rather than buildings that will not last as long as their architects? If the reuse of contemporary construction materials is minimal (about as far removed as you can get from the traditional approach of robbing out stone-based structures in their entirety) then longevity is the most logical alternative.

3 Recycle

It is becoming possible to both recycle other waste into concrete-based building materials and use concrete itself as a secure storage for greenhouse gases. A Canadian company called CarbonCure has developed a technique for permanently sequestering carbon dioxide in their concrete by converting it into a mineral during the manufacturing process, with the added benefits of increasing the strength of the material while reducing the amount of cement required.

As for recycling waste material as an ingredient, companies around the world have been developing light-weight concrete incorporating mixed plastic waste, the latter comprising anywhere from 10% to 60% of the volume, particularly with the addition of high density polyethylene.

For example New Zealand company Enviroplaz can use unsorted, unwashed plastic packaging to produce Plazrok, a polymer aggregate for creating a concrete which is up to 40% lighter than standard material. In addition, the same company has an alternative to metal and fibreglass panels in the form of Plaztuff, a fully recyclable, non-corroding material which is one-seventh the weight of steel. It has even been used to build boats as well as land-based items such as skips and playground furniture.

Therefore what might appear to be an intractable problem appears to have a variety of overlapping solutions that allow sustainable development in the building and civil engineering sector. It is somewhat unfortunate then that the conservative nature of these industries has until recently stalled progress in replacing a massive pollutant with much more environmentally sound alternatives. Clearly, green architecture doesn't have to be the sole prerogative of the driftwood dreamers; young entrepreneurs around the world are seizing the opportunity to create alternatives to the destructive effects of construction.