Sustainability – Page 9

Counting on … day 90

19th April 2024

How sustainable is wind power?

The following comes from a report by the German broadcaster, Deutsche Welle (DW).

“On average, wind turbines are operated for about 25 years. During this time, they generate 40 times more energy compared to the energy required for the production, operation and the disposal of a wind power plant.

“So-called upstream emissions, generated mostly through the production of carbon-intensive steel and cement, are included in the overall carbon balance of a wind turbine’s life cycle.

An onshore wind turbine that is newly built today produces around 9 grams of CO2 for every kilowatt hour (kWh) it generates, according to according to the UBA. A new offshore plant in the sea emits 7 grams of CO2 per kWh.

“Compared with other technologies, wind power does well in terms of carbon emissions. By comparison, solar power plants emit 33 grams CO2 for every kWh generated. Meanwhile, power generated from natural gas produces 442 grams CO2 per kWh, power from hard coal 864 grams, and power from lignite, or brown coal, 1,034 grams.” (1)

But what about the renewability of the turbines? Can their component parts be recycled so conserving the materials used? Wind turbines have a lifespan of 30+ years. At present the number being decommissioned is small but will grow – DW suggests that by 2050 up to 50,000 wind farms in Germany alone will need replacing. Whilst to some extent the concrete for the bases can be crushed and recycled as hardcore etc, and the steel and other minerals from pylons can be recycled, recycling the blades is less easy as they are a composite of glass fibre, plastic, carbon etc. Old blades may end up in landfill. However – “The first recyclable rotor blades for large offshore plants are currently being produced in Denmark. By 2030, the plant constructor Siemens Gamesa plans to only sell recyclable rotor blades: from 2040 the production of the company’s wind power plants is expected to be completely carbon neutral.” (1)

Nevertheless, wind power is one of the least environmentally damaging sources of energy.

https://www.dw.com/en/how-sustainable-is-wind-power/a-60268971

Counting on … day 89

18th April 2024

How Renewable are Renewables?

Many things are renewable as in they can be naturally replaced – timber is a renewable resource in that for every tree used/ consumed, another tree can be grown. Water is a renewable resource in that once used it can be recaptured and reused: this might be through the natural water cycle of evaporation, transpiration, condensation and rainfall, or through collecting and cleaning waste water for further use. Fish for use as food is a renewable resource – this supply of food is maintained through the natural reproductive processes of the fish.

However the renewability of things isn’t necessarily limitless.

If oceans are overfished, the rate at which new fish are born and mature will not keep pace with the rate at which fish are caught. Eventually there will be no fish.

If trees are felled faster than the rate at which new trees reach maturity – which can be 40 to 150+ years depending on the species – the landscape will become deforested.

If an ecosystem is not maintained, more can be lost through evaporation in a locality than falls as rain. Without forests in the middle of large continents, rainfall in these areas would be negligible reducing the landscape to desert. If rainforests are cleared, rainfall in those areas will be diminished reducing the landscape to bare earth.

Solar energy is a renewable energy source – the sun is constantly producing heat – as is wind, as the earth’s weather system continues to be generate wind. (Sometimes resources such as sunshine, wind, tides and geothermal energy are known as perpetual resources).

But whilst solar and wind energy are constant/ renewable, the means by which we capture that energy may not be as readily replaced. Solar panels that convert the sun’s energy into electricity are made of non-renewable minerals – silicon, silver, aluminium, and copper. Wind turbines that capture the wind’s energy converting it into electricity are made of large amounts of non renewable materials such as steel and carbon fibre.

The source of the energy is renewable but not always the means by which we capture the energy.

Here is an interesting blog describing how solar panels are made – https://blog.ucsusa.org/charlie-hoffs/how-are-solar-panels-made/

and wind turbines – https://blog.ucsusa.org/charlie-hoffs/how-are-wind-turbines-made/

Counting on … day 88

17th April 2024

Green steel and cement alternatives

Steel, cement and concrete are major contributors to global climate emissions using manufacturing process that are challenging to green. Therefore one approach to safeguarding the environment is to reduce the use of new steel, cement and concrete.

This could be by not wantonly discarding things before the end of their lifespan. Where I live, it is not infrequently that someone will buy a house only to knock it down and replace it with a new one. This unnecessarily adds to local carbon emissions. The same can also be true of commercial buildings. Simply demolishing an office building to replace it with another is a poor use of resources.

Where buildings or other structures are of necessity demolished, the prudent use of resources would see the different building materials being salvaged and reused. Equally before demolishing a structure, consideration could be given to re-purposing the building – upcycling!

The same approach of making full use of an item over its lifespan could equally apply to vehicles, domestic appliances, etc.

When building new structures, alternative materials with a lower carbon footprint can be used. This might be using timber for beams and columns, straw for insulation, compressed clay for bricks as well as recycling materials from other buildings. However if using naturally renewable resources such as timber, there has to be an awareness of the time frame and forwarded planning needed to ensure an ongoing supply of such materials. Trees may need to be up to 80 years old before being used to create structural building elements – and that timescale also implies large areas of land being set aside for trees (which is not a bad thing but needs to be planned).

Did you know you can buy bicycles made with a bamboo frame? – https://www.nethambamboobikes.co.uk/

Counting on … day 87

16th April 2024

Green cement – part 2

As part of the need to reduce all greenhouse gas emissions to address the climate crisis, reducing emissions from cement production is essential.

50% of the emissions come from the release of carbon dioxide as a byproduct during the clinker making process. One solution is carbon capture- capturing the CO2 before it escapes into the atmosphere, pressurising it to a liquid which is injected into rock strata deep underground. This technology has yet to be developed for use at an industrial scale.

Another solution is to replace the limestone with an alternative that produces less CO2 – such as magnesium oxide mixed with magnesium chloride solution. However such alternative cements may not have all the attributes of cement when in use – different construction methods may be needed.

40% of the emissions are attributable to the energy needed to heat the clinker kilns. Switching to renewable energy to replace coal is one solution but requires considerable investment in green electricity production and distribution.

Using materials other than limestone – such as volcanic rock – that can produce clinker at lower temperatures is another possible solution. Another alternative is to replace a proportion of the cement with an alternative binder such as ground granulated blast furnace slag or pulverised fly ash. Again this may alter the properties of the cement and require different construction methods.

10% of the emissions comes from energy used in mining and transporting the raw materials. Energy efficiency and the use of renewable energy will be a way forward.

Further reading –https://theconversation.com/green-cement-a-step-closer-to-being-a-game-changer-for-construction-emissions-126033

(https://theconstructor.org/concrete/green-cement-types-applications/5568/

Counting on … day 80

5th April 2024

Green Steel

Steel manufacturing produces more CO2 than any other heavy industry, comprising around 8% of total global emissions.

Traditionally steel is made in a blast furnace where the iron ore is he@ted at high temperatures together with coal. As the coal burns it produces carbon monoxide which bonds with and removes oxygen in the iron ore so purifying it to produce metallic iron. The carbon monoxide binding with oxygen becomes carbon dioxide and is one of the main sources of carbon emissions. Other sources of emissions will vary depending how the furnace is heated etc.

The industry is developing various ways of producing steel without – or with reduced – carbon dioxide emissions – known as green steel.

Replacing coal with hydrogen: Green steel can be produced by using hydrogen to remove the oxygen from the the ore – producing water (H2O). Ideally this would be green hydrogen – ie hydrogen produced using renewable energy. This method of producing steel requires heating the furnace to a higher temperature.

Reusing existing steel: steel can easily be recycled in arc furnaces powered by electricity – which ideally would be electricity from renewable energy sources with no carbon dioxide emissions.

Around 30% of the world’s steel is made from recycled steel. However steel cannot be recycled endlessly without loss of quality. Each time it is recycled the proportion of unwanted elements such as copper, nickel and tin increases. On the other hand steel has long in-use life which means that the amount of steel made available for recycling does not at present keep up with the growing demand for more steel. Our modern economies are big users of steel!

(For more detail see https://theconversation.com/green-steel-is-hailed-as-the-next-big-thing-in-australian-industry-heres-what-the-hype-is-all-about-160282)

Which ever form of green steel is produced, the availability of large amounts of renewable energy is going to be critical.

As important will be the way the transition is managed as furnaces are large and highly expensive pieces of kit – ie needing substantial investment – and can take years to install which in some instances has led to workers being laid off – as is proposed at the Tata steel works in Port Talbot. (https://www.theguardian.com/uk-news/2024/mar/25/tata-port-talbot-job-losses-labour-subsidy?CMP=Share_iOSApp_Other).

Other important issues to address are how steel is used – with product design ensuring a long life, whether other materials could be used – timber for example in building construction, and how effectively scrap steel is collected and recycled.

Further reading – https://www.bbc.co.uk/news/business-64538296

Counting on … day 78

3rd April 2024

Biofuels are fuels derived from biomass such as plant material, food waste, algae, or animal waste. There are two forms of biofuel –

“Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as maize, sugarcane, or sweet sorghum. Cellulosic biomass, derived from non-food sources, such as trees and grasses, is also being developed as a feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form (E100), but it is usually used as a gasoline additive to increase octane ratings and improve vehicle emissions.

And “Biodiesel is produced from oils or fats using transesterification. It can be used as a fuel for vehicles in its pure form (B100), but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles.” (https://en.wikipedia.org/wiki/Biofuel)

Brazil is the largest producer of bioethanol and the EU is the largest producer of biodiesel.

Both forms of biofuel differ from fossil fuels in that they are produced from organic materials being grown now as opposed to using organic materials that were decomposing millions of years ago.

Both produce greenhouse gas emissions but less than do fossil fuels. Biofuels may be made using only waste materials, but often are made from crops that have been specifically grown for this purpose. This may have the affect of diverting land that would otherwise be used for growing food, or may involve deforestation to create new crop lands.

Drax power station which burns timber as a biofuel to generate electricity uses wood pellets. Although wood pellets can be made from waste wood, most of the pellets that are burnt at Drax are made from whole trees that were once growing in virgin forests in South Carolina and British Columbia. These are then imported to the UK. For more information- https://www.bbc.co.uk/news/science-environment-68381160

Counting on … day 75

27th March 2024

Agroforestry offers another approach to farming that enables the long term increased sequestration of carbon dioxide. Agroforestry has two main forms:

“Silvo-pastoral agroforestry: which means the grazing of animals under trees. The animals enrich the soil while the trees provide shelter and fodder for the animals.

Silvo-arable agroforestry: where crops are grown beneath trees, often in rows which are large enough for a tractor to tend to the crops without damaging the trees. This is farming in 3D, the trees and the crops occupy different levels above ground, and also below ground where the tree roots will reach down deeper than the crops.”(1)

The additions of trees in the farm enhances the amount of carbon dioxide that is being . At the same time the practice also benefits the condition of the soil. “Tree roots reach deep into the ground, releasing much-needed carbon into the soil. They cycle nutrients and bind the soil together, preventing it from being eroded by the wind or the rain.”(1)

(1) https://www.soilassociation.org/causes-campaigns/agroforestry/what-is-agroforestry/

Counting on … day 72

22nd March 2024

Carbon sequestration is a formal name given to the processes by which carbon is captured from the atmosphere and stored on a long-term basis. Such long-term storage might include peat bogs, forests, kelp beds etc and may be referred to as ‘carbon sinks’.

Carbon sequestration can be used as a means of mitigating the effects of climate change. This can be biologically by, for example, planting more forests, restoring peat bogs and wetlands, and re-establishing kelp meadows. This natural sequestration can be enhanced, in the case of forests, by using felled timber to make items such as buildings, furniture etc and keeping those items for hundreds of years. However growing trees for timber needs to be carefully managed to a) maximise the carbon captured by the growing tree, and b) to maximise the flourishing of biodiversity.

Carbon can also be sequestered geologically if the CO2 can be captured eg from a cement factory. Then the CO2 “can be compressed to ≈100 bar into a supercritical fluid. In this form, the CO2 could be transported via pipeline … and injected deep underground, typically around 1 km, where it would be stable for hundreds to millions of years.” (https://en.wikipedia.org/wiki/Carbon_sequestration)

Counting on … day 71

21st March 2024

The carbon cycle

The earth’s systems have various ways of absorbing and using carbon dioxide in such a way as to enable life to flourish. Plants absorb carbon dioxide as part of the process of photosynthesis storing the carbon as cellular material in their leaves, branches etc. Plants release carbon dioxide back into the atmosphere as they respire – breathe. A living growing plant absorbs more carbon dioxide than it releases. When the plant dies, the carbon that has been stored as leaves and branches etc slowly decays – breaks down – and the carbon returns to the atmosphere as carbon dioxide. This is as true of water and marine plants as it is true of land plants.

(For a short video describing how trees absorb and use carbon – https://www.woodlandtrust.org.uk/climate-change/carbon-trees/)

Soil in part is made up of dead plant and animal material which decays slowly overtime. Soil is therefore a storer of carbon.

The seas and oceans also contain carbon dioxide that is dissolved in the water. This carbon dioxide cycles through the water as marine plants take in, store and release the carbon as they grow. Marine waters and the layers of sediment at the bottom of the seas and oceans store carbon in the same way as does soil.

This brings us back to an earlier post about how much carbon dioxide there is in the atmosphere (measured in part per million) and the rate at which that concentration is increasing due to human activities – https://greentau.org/2024/02/19/counting-on-day/

Counting on … day 70

20th March 2024

The geological history of oil and gas.

“The formation of oil takes a significant amount of time with oil beginning to form millions of years ago. 70% of oil deposits existing today were formed in the Mesozoic age (252 to 66 million years ago), 20% were formed in the Cenozoic age (65 million years ago), and only 10% were formed in the Paleozoic age (541 to 252 million years ago). This is likely because the Mesozoic age was marked by a tropical climate, with large amounts of plankton in the ocean.

“The formation of oil begins in warm, shallow oceans that were present on the Earth millions of years ago. In these oceans, extremely small dead organic matter – classified as plankton – falls to the floor of the ocean. This plankton consists of animals, called zooplankton, or plants, called phytoplankton. This material then lands on the ocean floor and mixes with inorganic material that enters the ocean by rivers. It is this sediment on the ocean floor that then forms oil over many years”.

The dead plankton, plus algae and bacteria form an organic rich mud.
If the mud remains in an anoxic environment – lacking in oxygen such as stagnant water – it does not decompose and so retains its carbon content.
This anoxic environment becomes embedded by subsequent layers of mud, compressing the carbon rich layer into an organic shale.
Overtime the shale sinks as more layers are added. At a depth of 2 to 4km the temperatures from the earth’s core plus the increased pressure converts the organic shale to oil shale.
If the temperatures at this depth are between 90 and 160C this oil shale is transformed into oil and natural gas. This will either seep upwards being lighter than water, or maybe sealed in by subsequent layers of impervious rock.

(https://energyeducation.ca/encyclopedia/Oil_formation)

Again it is mind blowing to reflect that these oil and gas deposits that took millions of years in the making, are now being burnt at an annual rate of 6.6 billion tonnes, such that we have 47 years of reserves remaining – should we be foolish enough to want to burn them.(https://www.worldometers.info/oil/)

We should keep in mind that the IEA warns that a cannot risk developing and burning new oil and gas reserves without exceeding the 1.5C global warming limit.