Category: Environment

The wastewater released from industry often contains high levels of toxic heavy metals, which can kill organisms, damage ecosystems, and accumulate in the foodchain. Electroplating, lead smelting, mining, and countless other processes produce enormous volumes of such wastewater.

In a perfect world, remediation would be powered by a renewable energy supply, there would be no solid waste to dispose of, and the heavy metal contaminants could be recycled back into the industrial process with minimal losses. That would be industrial Utopia, of course, but something close might exist if scientists can genetically modify aquatic plant species to grow quickly and soak up heavy metal ions from wastewater.

So-called phytoremediation technology has been used as an economical and eco-friendly option for treating wastewater for several years. It could have an even more significant impact on industry in the developing world, as genetic engineering programs mature.

“Phytoremediaton technologies involving the use of aquatic plants can be a better alternative to traditional/conventional technologies for treating wastewater in terms of low capital investment, minimum human power, less damage to environmental resources and limited energy consumption,” says Bhupinder Dhir of the Department of Environmental Biology, at the University of Delhi, India. He points out that the biosorption potential of aquatic plants should be more keenly explored for developing remediation methods.

Crucial to success is to grow wetland and other aquatic plants that produce a large biomass quickly even in highly toxic wastewater, but also express high levels of metal-sequestering proteins and other factors. For instance, over expression of the plant enzymes cystathionine gamma synthase and selenocysteine methyltransferase in aquatic plants could quickly soak up heavy metals. Species such as Spartina and Typha are already under investigation as transgenic wetland plants carrying Mer genes, which can absorb mercury from contaminated aquatic ecosystems.

However, all this work, still leaves one major problem: what to do with the contaminated plant biomass once the wastewater has been cleaned up?

“The decomposition of metal loaded plant biomass with passage of time raises an issue of major concern among the scientific community,” says Dhir. “Appropriate treatment of plant biomass retaining high levels of heavy metals before disposal is important to prevent further threat to the environment.” He suggests that post-harvest treatment is essential, perhaps involving composting and the associated reduction in volume.

Phytoremediation may eventually offer a leafy green possibility for cleaning up industrial wastewater even if we have not quite reached Utopia. However, there also has to be a way to retrieve the heavy metal leachate from this process. Incineration, pyrolysis, and biogas production are all being considered for the end products of phytoremediation. The technology will only become acceptable once a safe way to extract the heavy metals from the biomass and then safely dispose of the residue is found. And to be environmentally worthy that also has to be both energetically and economically viable.

Bhupinder Dhir (2010). Use of aquatic plants in removing heavy metals from wastewater Int. J. Environmental Engineering, 2 (1/2/3), 185-201

It’s Blog Action Day 2009 and the subject this year is Climate Change. So, here are a few resources for readers seeking out climate information:

IPCC – Intergovernmental Panel on Climate Change – The IPCC assesses the scientific, technical and socio-economic information relevant for the understanding of the risk of human-induced climate change.

EPA – The US EPA Climate Change site provides comprehensive information on the issue of climate change and global warming in a way that is accessible and meaningful.

BBC Weather Centre – Aims to inform people about the potential changes in our weather over the next 100 years.

RealClimate – A commentary site on climate science by working climate scientists for the interested public and journalists.

Island of Doubt …the struggle between the power of rational discourse and the scientific method on one hand, and the forces of superstition and dogma on the other. But mostly about climate change.

Climate Feedback – Blog hosted by Nature Reports to facilitate lively and informative discussion on the science and wider implications of global warming.

Recent climate change news

• An Ice Artist’s Poignant Plea to Halt Global Warming
• Activists Sue Texas to Restrict Greenhouse Gases
• Coral Bleaching Creates a Vicious Cycle of Further Bleaching and Disease
• Big Business Gets Behind the Climate Bill
• China: US is sabotaging Copenhagen climate treaty by ‘changing Kyoto rules’
• World Briefing | Asia: Maldives: Bring the Waterproof Pens
• Remember the ozone layer? It’s still there

Reduce, re-use, and recycle. Just one of the countless mantras of the twenty-first century that we are told will save the planet. Of course, my grandmother used to put it far more succinctly and in a much more accessible form: waste not, want not.

Now, we have carbon footprints, emissions targets, and landfill directives, that are meant to govern what we should be doing in order to mitigate environmental devastation. Of course, we try to reduce our consumption and I encourage everyone to sign up to the 10:10 campaign or its local equivalent where you are.

If you can, get hold of, or borrow an energy meter that gives you a display of your electricity consumption and lets you home in on hidden waste, specifically those devices on standby that you should really switch off at the outlet. I’m even trying to convince the rest of my family, who should know better given grandma’s mantra, that we should be cutting down on waste and turning out lights, boiling only enough water, and avoiding car journeys when we can.

But, then I read about the trillions of plastic bags produced each year, the billions of drinks containers, and all those incandescent light bulbs that are suddenly redundant thanks to new laws aimed at reducing energy consumption and forcing us to switch to compact fluorescent tubes…are our miniscule efforts worth it in the face of such environmental threats?

What about metal bottle tops, every liver-defying beer we crack open, every tooth-rotting cola drunk, usually means a glass bottle and a bottle top? The glass is relatively easy to recycle, unless its brown or green, in which case it will most likely be crushed for hardcore for building roads. The crown cap is a mixed metal product usually with a polymer layer and paint, so not quite so easy to extract and recycle, at least until now. Currently, the recycling processes for metal bottle tops work through millions of tonnes but are inefficient, wasting energy and losing a large amount of the metal. Moreover milling and grinding affect the metal morphology in a detrimental manner making further processing of the material into a useful form difficult.

Mahmoud Rabah of the Chemical and Electrochemical Laboratory, at the Central Metallurgical R&D Institute (CMRDI), in Cairo, Egypt, and his colleagues are working towards a method for recycling metal bottle tops that could take this huge problem out of the waste equation and provide a source of recycled aluminium.

Rabah explains that standard magnetic extraction allows iron tops to be separated from aluminium tops and once melted with a flux material (sodium borate-sodium chloride mixture), other impurities can be scraped off by flotation techniques, the team explains, and hydrochloric acid leeches out the aluminium. Paint breaks down to titanium dioxide on heating at 750 Celsius for just half an hour. The team then found that they could create standard aluminium alloy by addition of a primary master alloy and so recover almost all (96.8%) of the aluminium from a bottle top waste stream. Sounds like a plan to me, but…

…there always remains the problem of balancing the energy books. The extracted aluminium alloy is valuable, certainly. Recycling aluminium from the cans themselves as opposed to bottle tops uses about 5% of the energy needed to extract virgin aluminium from bauxite, the mined aluminium ore. But, recycling aluminium bottle tops may not be quite so energy efficient and further studies are now needed to discover whether it will not only be commercially viable but whether the extraction is environmentally sensible. There may be some other less energy-intensive way to reuse waste bottle tops, after all.

I asked Rabah about the issues and he told me that discussions have been started with the three foreign companies working in Egypt that collect, sort and sell household waste in the greater Cairo region. One of the first problems they face is how to sort the 18-tonne sample batches because facilities do not yet exist to carry out this critical task. Manual separation has been suggested but that is practically very tedious and labour intensive.

However, with grandma’s mantra in mind, finding a way to make the endless stream of waste bottle tops, and those already in landfills across the globe, a viable source of metal should be found. Think about it, landfills packed with metals, plastics and other commodity materials, albeit in impure and mixed forms, could become the mines of the future once extraction techniques are made economically and energetically viable.

Mahmoud A. Rabah (2009). Recovery of aluminium alloys and some valuable salts from spent bottle covers Int. J. Environment and Waste Management, 5 (1/2), 194-210

Biofuels are not much better than fossil fuels in terms of the impact on atmospheric pollution levels and effects on climate change, according to Mark Jacobson professor of civil and environmental engineering at Stanford University. This is especially true when making claims about the sustainability of biofuels in comparison with hydrogen fuel cells and battery-driven electric vehicles charged up using solar, wind, tidal or other truly renewable energy sources.

To quote from his web page, the main goal of Jacobson’s research is to…

…understand physical, chemical, and dynamical processes in the atmosphere better in order to address atmospheric problems, such as climate change and urban air pollution, with improved scientific insight and more accurate predictive tools. He also evaluates the atmospheric effects of proposed solutions to climate change and air pollution, examines resource availability of renewable energies, and studies optimal methods of combining renewables.

In order to accomplish these important goals Jacobson has developed and applied various models to simulate gas, aerosol, cloud, radiative, and land/ocean-surface processes that could give scientists and engineers a much more overarching perspective on the climate than other simpler models.

Jacobson points out that the use of biofuels, particularly ethanol, has expanded in the last few years, although in South America biofuels have been popular and successful for decades. This more recent and rapid expansion of biofuel use in transport across North America and elsewhere is based on the notion that by replacing fossil fuels with biofuels we may somehow ameliorate global warming and air pollution. After all, he growing plants absorb carbon dioxide from the atmosphere, they are then converted into biofuels, which are burned in modified vehicle internal combustion engines, which releases the carbon dioxide into the atmosphere again, where it is used by the next generation of biofuel crop plants to grow and so on.

This claim is still being hotly debated, especially given the impact on agriculture and the environment of turning over vast tracts of land to biofuel crops rather than growing food. However, Jacobson believes that, “the real comparison should be between biofuels and other emerging technologies.” He reports that corn-E85 (85% ethanol/15% gasoline) and cellulosic-E85 both degrade air quality and climate by up to two orders of magnitude more than electric vehicles ultimately powered by solar photovoltaic cells, wind, geothermal, hydroelectric, wave, or tidal power. “As such, the use of cellulosic or corn ethanol at the expense of the other options will cause certain damage to health, climate, land, and water supply in the future,” he asserts.

Moreover, the land required for cellulosic-E85 may also exceed that of corn-E85 and the land required for both will exceed that required for the footprint on the ground of wind powering battery electric vehicles by a factor of 500,000 to 1 million, adds Jacobson. He suggests that we should be considering very carefully the notion that replacing fossil fuels with biofuels could save us from catastrophic climate change given that this is not only unlikely, but will also have a negative impact on land and water supply relative to genuinely renewable energy sources.

I asked Jacobson for his thoughts on how vested interests might be persuaded that biofuels are no panacea. “The biofuels interests will go out of their way to dismiss or distort results from any study that comes out that makes their product look bad,” he told me. “It is mostly politicians and the public who can be persuaded,” he added. “The best approach is to focus on what is better, such as electric hydrogen fuel-cell vehicles powered by renewables, and to try to push people more in that direction.”

Mark Z. Jacobson (2009). Effects of biofuels vs. other new vehicle technologies on air pollution, global warming, land use and water International Journal of Biotechnology, 11 (1/2), 14-59