Geo-Engineering: For or Against?

Having written on the topic of Geo-Engineering for the past few months, I feel that I have developed my understanding of many of the issues surrounding this topic. I started this blog being heavily sceptical of all forms of geo-engineering; since then I have warmed to certain forms.

Personally, I think that solar geo-engineering methods are far too risky; they have many more downsides than upsides. Forms of geo-engineering that involve carbon dioxide removal is where my greatest support lies. These methods aim to reduce the cause of anthropogenic climate change and despite working slowly, have fewer risks and can operate alongside the reduction of greenhouse gas emissions.

Determining whether to use geo-engineering depends on a form of cost-benefit analysis bringing together a variety of factors. Use of geo-engineering involves questions over finances, environmental impacts, political and military motives, feasibility, time scale and unexpected consequences. Only by assessing the multitude of factors can it be possible to determine if any of the geo-engineering techniques are suitable.

I am more positive about geo-engineering than when I started this blog but further research into the impacts of different methods is desperately needed as there is currently insufficient knowledge to make a clear and informed decision.

Why Geo-Engineering may not be the solution

Up until now I have focused on different forms of geo-engineering, discussing both the benefits and drawbacks of these methods. In this post I wish to look into some of the reasons why Geo-Engineering as a whole may not be a feasible solution to anthropogenic climate change. This blog will focus a few key areas, these being: the effect Geo-Engineering can have on regional climate, human error, the neglect of cutting emissions, possible catastrophe,alternative uses of Geo-Engineering (commercial and military) and controlling the temperature.

Effect on regional climate

Geo-Engineering can have a profound effect on regional climate including altering rainfall patterns, surface albedo and local temperatures. A paper from 2016 investigated the effects of solar dimming (reducing the amount of sunlight reaching Earth) through geo-engineering on crop production. Although not fully understood, a number of crop-climate simulations have estimated that crops would be negatively affected by changes in solar radiation and rainfall patterns caused by solar dimming. Importantly, this paper concluded that despite geo-engineering impacting crop yields, when the geo-engineering is turned off, the crops recover to previous levels. The fact that geo-engineering methods do not have lasting effects on crops is beneficial but this does not ignore the fact that crop yields in certain areas may decline under the effect of certain geo-engineering schemes. This must be considered where determining whether to implement certain programmes.

Human error and possible catastrophe

Human miscalculation and societal problems could also bring about major problems for geoengineering. It has been established that, with certain solar geo-engineering techniques, a halting of the process could accelerate warming faster than we are currently seeing. Baum and Maher Jr.(2013) discussed the idea of a double catastrophe linked to stratospheric aerosols. The possibility of political conflict or war leading to the interruption of aerosol injection could destabilise the climate leading to rapid warming. In such instances, the use of geo-engineering could have more negative impacts than business as usual and the reliance on sustaining aerosol injection leaves the planet vulnerable to unintended and unexpected consequences.

Neglect of cutting emissions

Funding and focus on geo-engineering techniques could mean that cutting emissions is neglected. Some have suggested that geo-engineering should be used alongside cutting emissions and that reducing GHG emissions should be the priority. In practice however, this may not be the case as funding would then have to be divided between the two, meaning the technology progresses at a slower rate. Cutting GHG emissions is the most straightforward and lowest risk strategy for reducing the effects of climate change and therefore it may not be necessary to employ a riskier strategy such as geo-engineering. Many forms of geo-engineering are only short term solutions (particularly solar geo-engineering) and they are not understood well enough. Humanity needs to react to climate change now and the most effective and straightforward way to do this is through reducing emissions. Geo-engineering methods would only distract from this objective.

Figure 1: Should we be focusing on cutting greenhouse gas emissions?

Alternative uses of Geo-Engineering

Worryingly, the purpose for carrying out Geo-Engineering methods may not be centred on addressing climate change. Geo-Engineering could also be used for financial gain as well as military use. There is evidence that in the mid-20th century, global superpowers were exploring methods for altering climate to gain an advantage in battlefield warfare. There are existing global agreements such as the ‘Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques’ that was signed in 1976 but it is hard to see no military use of geo-engineering in some form in the future. Many companies supplying geo-engineering may find ways of making their technology more expensive to national governments thus profiting greatly from geo-engineering rather than using it for the greater good. The commercialisation of geo-engineering would set a dangerous precedent that could cause more problems than benefits. I believe that in order to be effective, geo-engineering must be solely used to modify climate as a response to climate change rather than for military or financial gain but realistically it would be very difficult to achieve this.

Controlling the temperature

There are also political issues surrounding the controlling of global temperatures. For example, countries at higher latitudes may want a warmer climate to allow them to grow more crops for export but this may adversely affect countries at lower latitudes. This brings about big debates between nations on what temperature to set climate. Every country would have an agenda and therefore agreeing a ‘temperature setting’ would be difficult and very time consuming. This is time that the planet doesn’t have and therefore geo-engineering may not be the best solution for climate change.

To sum up, it is clear that there are many potential drawbacks to geo-engineering as a whole. Despite this, I still feel that certain methods should not be ignored entirely. If they can be effectively implemented in such a way that they are low risk, work alongside reducing GHG emissions and do not have the potential to be exploited then it is worthwhile considering them as an option. This is a lot to expect but only once these criteria are met do I feel that certain geo-engineering methods should be considered for implementation.

Geo-Engineering: a cost-benefit analysis

Writing frequently around the topic of geo-engineering to modify Earth’s climate either through altering atmospheric carbon or by reducing the solar radiation reaching Earth, it has become clear that the whole issue revolves around a cost-benefit analysis. All geo-engineering techniques bring different costs and benefits and it is up to humans to analyse, assess and come to conclusions on whether any of the methods are suitable or whether business as usual is less risk. Costs can be more than just financial, they can include unintended consequences, time and other environmental impacts. I have advocated the use of carbon dioxide removal techniques because they are low risk but many may support the use of solar geo-engineering because of the greater benefits. This discussion and debate can only be valuable in attempting to determine human response to anthropogenic climate change be it low risk or high reward.

Solar Geo-engineering: research needed

As you may be aware by now, I am fairly sceptical about solar geoengineering techniques on the whole. Having focused heavily on carbon dioxide removal techniques thus far, I felt it would be fair to consider some of the solar geoengineering methods despite my negative opinions towards them. The Youtube video in this post is a Ted Talk on the need for a proper research programme for solar geoengineering techniques. It puts across a lot of the pros and cons of solar geoengineering methods so is well worth a watch if you have 15 minutes spare.

The key message I got from listening to this talk, which was also the objective of the talk, was not that solar geoengineering is necessarily a good (or bad) idea but the fact that there is a desperate need for a serious research programme into the effects of these different schemes. At the moment, there is simply not enough information on the potential benefits and risks. The need for a proper research programme is key to avoiding making ill-informed decisions that could be disastrous.   

Solar geoengineering has been proposed as a way to avoid climate tipping points. This is achieved through reducing the amount of solar radiation reaching Earth, leading to a lowering of global temperatures. There are a number of different methods to achieve this which are described in detail in the Caldeira et al. (2013) paper. The problem with all solar geo-engineering methods is that they do not alter the levels of carbon dioxide in the atmosphere despite decreasing global temperatures. This is potentially risky as if a solar geo-engineering technique were to fail, temperatures would rise at an even faster rate than we see presently.

Another major drawback of solar forms of geo-engineering is the costs of implementation. Injecting sulfate aerosols into the stratosphere is no different to other forms in this regard with high financial costs. In addition to the actual pumping of the sulfur dioxide into the atmosphere, there are high costs associated with the production and transport of this gas. One suggestion is to only use stratospheric aerosols over the Arctic to reduce sea ice melting. This would help to reduce the costs whilst still seeing significant benefits. All forms of geo-engineering are costly, both financially and in terms of climate risk which means humans must be certain of their impacts before attempting to implement them.

The biggest reason to avoid solar geo-engineering is the high risks associated with many of the methods. One method I do see as feasible in the short term is roof whitening. A paper by VanCuren (2012) highlighted the radiative forcing benefits of roof whitening in California, USA. The paper concluded that there could be significant benefits of this form of geo-engineering in California but these benefits are spatially variable depending on climate.

As it is clear to see, I feel that the drawbacks of many solar geo-engineering methods far outweigh the benefits and this is why in this blog I have chosen to focus on the more feasible and cheaper carbon dioxide removal techniques. They may not be as effective at reducing climate change in the short term but at least they are not as risky as many of the solar geo-engineering methods proposed. 

Carbon Dioxide Removal over Solar Geo-Engineering

At this point, I feel it necessary to explain why this blog has heavily focused on the forms of Geo-Engineering that involve Carbon Dioxide Removal (CDR) rather than Solar Geo-Engineering techniques.

The first is that CDR methods address the problem at the root of climate change, the carbon produced through anthropogenic emissions rather than attempting to deal with the issue in a roundabout way by reducing the amount of solar radiation reaching Earth. This ties in neatly with the second reason, there are likely to be fewer unintended consequences associated with CDR techniques. By reducing the atmospheric levels of carbon, CDR methods are attempting to reverse the current trend to prior levels that have already been experienced and studied rather than shifting our climate in an unknown way. Unexpected shifts could lead to further problems that could be worse thanthe current situation.

Another justification for CDR methods is that there are other indirect benefits. Removing carbon dioxide from the atmosphere can help to reverse the current trend of ocean acidification due to the ocean-atmosphere flux, benefiting marine species such as coral which are under the threat of extinction.

Carbon Dioxide Removal approaches are also easier to control than Solar-Engineering methods. It is relatively easy to stop capturing atmospheric CO₂ or stop ocean fertilisation compared to removing large sun reflectors from space or removing chemicals pumped into the upper atmosphere. In addition, pumping aerosols into the upper atmosphere could lead to ozone depletion.

Furthermore, there is likely to be less human error involved in CDR practices in comparison to Solar Geo-Engineering methods because atmospheric carbon dioxide has been widely studied whereas the implications of altering the amount and distribution of solar energy reaching Earth is understood to a lesser degree and because of this makes Solar Geo-Engineering techniques far more risky despite possibly bringing about faster climate responses. Solar Geo-Engineering is seen as having greater issues surround governance, equity and ethics that also create other disincentives for implementing some of these concepts.

Figure 1: Solar Geo-Engineering: (a) reflectors (b) stratospheric aerosols (c) cloud brightening
(d) increasing ocean reflectivity (e) reflective plants (f) roof whitening

Carbon Dioxide Capture: Part II

Carrying on from the last post, Carbon Dioxide Capture is a technique to prevent carbon dioxide from reaching the atmosphere in the first place as well as being a method to remove some of the existing carbon dioxide currently in the atmosphere. The previous post focused on the methods of this form of Geo-Engineering and this post will now look at the benefits, drawbacks and feasibility of this method. Carbon Dioxide Removal techniques are often thought of as longer term schemes compared to some of the solar geo-engineering methods suggested because removal of carbon dioxide is slow and therefore the response of climate is also slow. This needs to be considered when attempting to assess the feasibility of all geo-engineering schemes.

Figure 1: Carbon dioxide capture plant in Malaysia

One key positive of carbon dioxide capture is that the technology to achieve this is already available and in use presently. The processes involved in the capture of carbon dioxide in power plants can be easily applied to atmospheric carbon dioxide by capturing air and processing it. This means that the technology of this form of geo-engineering is far more advanced and more rigorously tested that those of other geo-engineering schemes that are still in the research phase. The option to implement this method is therefore possible in the short term as an attempt to begin to reduce carbon dioxide levels.

Evidence from Iceland has found that underground storage of carbon dioxide is much more promising than first thought. CO₂ pumped underground to volcanic basalt rock converted to a solid far more quickly than previously expected, just two years rather than hundreds to thousands of years. Even more positive is the fact that this rock type is widely distributed worldwide suggesting that this a viable method for storing the carbon dioxide captured from power plants and from the atmosphere. The conversion to solid is more beneficial than storing CO₂ underground as a gas due to the risk of leakages. This further advocates the implementation of carbon dioxide capture and storage as soon as possible.

Despite this, capture of existing atmospheric carbon dioxide would have limited effects on atmospheric CO₂ in the short term because of the ocean-atmosphere flux. This flux is the process by which carbon dioxide is exchanged between the ocean and atmosphere constantly. Around a quarter of carbon dioxide emitted by humans in the last two decades was taken up by the ocean. The oceans are therefore a key carbon ‘sink’ (store). By reducing the amount of carbon dioxide in the atmosphere, the ocean-atmosphere flux would increase the transfer of carbon dioxide from the oceans to the atmosphere – a process known as outgassing. This replacement of the carbon dioxide that had been taken out of the atmosphere therefore would not have significant impacts on climate change for a long period of time. This is not to say that in the short term it is not positive because the removal of carbon dioxide from the oceans would reverse the existing trend of ocean acidification that is threatening corals and other ocean species. Overall, atmospheric carbon dioxide capture would have an influence on climate change in the long term and help reduce ocean acidification in the short term which are both very positive.

Atmospheric carbon dioxide capture is unfortunately far less effective than capture in power plants. Therefore capture of past emissions would have much less impact on climate change. Atmospheric capture is less effective because the concentration of carbon dioxide in the atmosphere is only 0.04% compared to around 10% in power stations. This also makes it far less economically justifiable as CO₂ is costly to capture. There is great variation in the cost of carbon dioxide capture because there are a wide variety of factors at play such as plant size, efficiency, fuel cost, etc.. Despite this, I feel that with the current state of climate change and the expected increases in temperature and other changes associated in the future, the benefits of implementing such schemes both in power plants and for atmospheric capture outweigh the financial costs and the other more minimal environmental costs such as leakages from underground stores.

On the whole it is difficult to estimate the financial costs associated with carbon dioxide capture and storage at power plants and from the atmosphere because of the variety of different factors that play a role, most notably the method of carbon capture. One paper estimated that air capture devices could each capture around 400 tonnes of CO₂ per year. Despite being a relatively small amount, it could still have an impact.

To conclude, I believe there are significant advantages to the use of carbon capture in both power stations and atmospheric capture to reduce the amount of carbon dioxide added to the atmosphere in the future and existing carbon dioxide contributing to climate change. It would also be straightforward to suggest that the benefits of this form of geo-engineering heavily outweigh the negatives. Carbon capture, may be expensive to implement but I challenge anyone to think of a form of geo-engineering that is sufficiently effective that is inexpensive. In order to reverse the impacts of anthropogenic emissions, a large (and expensive) solution is needed. This is simply unavoidable. 

Carbon Dioxide Capture: Part I

I am not ignoring the solar engineering forms of geo-engineering entirely in this blog but at the moment I’m focusing on carbon dioxide removal (CDR) techniques as I feel these will have fewer unknown and unintended consequences because they aim to reverse the fossil fuel trend of adding carbon to the atmosphere and do not try to reduce solar radiation reaching Earth. Atmospheric Carbon Dioxide Capture is a form of CDR geo-engineering that I feel has great potential. This involves taking carbon dioxide out of the atmosphere through chemical reactions and storing it deep underground or using it in industry. Many authors do not consider the capture of carbon dioxide at power plants to be a form of geo-engineering because it is not dealing with carbon dioxide that has already been released to the atmosphere. I personally disagree with this and see the removal of carbon dioxide from power plants as a key way to reduce the effects of climate change into the future on a large scale which is the current objective of all geo-engineering techniques. However, if you hold the view that it is not a form of geo-engineering, the procedures of carbon dioxide removal in power plants mentioned in this article are still applicable to global atmospheric carbon dioxide removal (which is a form of geo-engineering). This is why I feel it is particularly important to write a post on these techniques. This topic will be divided into two posts, the first on the different methods being used and the second on the stores, benefits, drawbacks and feasibility of these techniques.

How does it work?

According to Metz et al. (2005) there are four basic systems for capturing carbon dioxide from fossil fuels and biomass. These are as follows:

1. Capture from industrial process streams
2. Post-combustion capture
3. Oxy-fuel combustion capture
4. Pre-combustion capture

The first of these has been operational for 80 years but the CO₂ captured is still added to the atmosphere as until now there was no reason to store it. This is very unfortunate as, if the incentive to store this carbon had started 80 years earlier, the human race would not be in such a dangerous and unpredictable climate change situation. Implementation of this method therefore seems very straightforward, with few changes needed. Post-combustion capture involves the capture of carbon dioxide from flue gases produced during the burning of fossil fuels and biomass. The CO₂ is then pumped back underground. Ox-fuel combustion capture is very similar to Post-combustion but pure oxygen is used in the combustion and therefore the flue gas is mainly CO₂ and H₂O which are easier to recycle. Finally, pre-combustion capture involves ‘reacting a fuel with oxygen or air and/or steam to give mainly a ‘synthetic gas (syngas)’ or ‘fuel gas’ composed of carbon monoxide and hydrogen.’ A catalytic converter, such as those used on car exhausts, can then be used to produce carbon dioxide and more hydrogen and this can then be separated by physical or chemical absorption leaving hydrogen-rich fuel which can be used in many systems such as boilers and gas turbines. The latter three methods all revolve around the idea of making combustion less polluting to the atmosphere.

The techniques for separating carbon dioxide are varied and each have their merits. The three main processes for separation are shown in Figure 1. The first technology I wish to discuss is called ‘Separation with sorbents/solvents’ (Diagram A in Figure 1). This involves bringing the gas into contact with a liquid absorbent or a solid sorbent that separates the carbon dioxide from the rest of the gas. The sorbent that is loaded with CO₂ is then transported to another vessel where it releases the carbon dioxide following a change in the environment (e.g. heating or increased pressure). This sorbent is then recycled to collect more CO₂ in a cyclical process.

Separation with membranes is a method whereby only certain gases are able to permeate through the membrane. The flow through the membrane is driven by pressure differences. There is currently research and development ongoing to manufacture a membrane suitable for the large scale capture of carbon dioxide. This means this method is less widely used at present.

Cryogenic distillation (Diagram C in Figure 1), describes the process by which gases are converted to liquid through compression, cooling and expansion and then are distilled to capture the CO₂. This form of CDR is currently being carried out at a large scale commercially which suggests that it has great potential.

Figure 1: Main separation process for carbon dioxide capture.

These three capture technologies highlight the different ways carbon dioxide is removed in power plants and during biomass burning. The methods here deal with the carbon dioxide at the source and therefore prevent the carbon from reaching the atmosphere and influencing climate change. Achieving this reduces the need for other extreme methods of geo-engineering that could lead to unintended negative consequences for climate. These systems can also be applied to the removal of carbon dioxide already in the atmosphere. However, due to the lower atmospheric concentrations of carbon dioxide in the atmosphere than in power plants suggests that the efficacy will be less for atmospheric carbon dioxide capture.

This concludes the first part on the topic of how carbon dioxide removal is carried out in power plants and from the atmosphere. The next post will continue on this topic but turn the focus to where the carbon would be stored once it has been captured. In addition to this, the post will look into the benefits and drawbacks to this form of geo-engineering and whether it is feasible as a method to reduce the effects of climate change at a large enough scale to be considered by governments worldwide.