Tag: Net zero

Net Zero and GHG Emissions

The aim of Net Zero GHG emissions is to stabilise global average temperatures, it is hoped that it can be achieved at 1.5C over pre-industrial levels. The calculation of CO2e for each of the GHG gases needs to take into account the impact of each of these gases upon global average temperatures. For CO2, it is quite simple: just take the quantum of the emissions themselves. 400 parts per million of CO2 equals 400 parts per million tonnes of CO2e. Since N2O has a half life of around 120 years, the normal calculation to convert to CO2e applies. In this case, 300 parts per billion of N2O equals 89 parts per million of CO2e. For the other gases a different calculation must apply. Since the other gases have a half life that significantly impacts their warming potential (methane has a half life of 9.5 years), we cannot just keep adding these warming potentials into our CO2e values. We have to take into account the progressive reduction in the atmospheric levels of these gases from previous emissions. For each year, we can (roughly) add the current emissions into CO2e, but we also have to deduct the losses into the atmosphere from previous years.

Net Zero from methane

For methane, we can simply deduct the losses attributable to the methane emissions in prior years.

  • Year -1: 4.75%
  • Year -2: 13.80%
  • Year -3: 21.99%
  • Year -4: 39.40%
  • Year -5: 36.11%
  • And so on into infinity.

If the world reduces the absolute value of methane emissions in each year, this gives us all a negative CO2e value that can be shared around amongst all nations. This will soften the required reductions in regard to continuing emissions of CO2 and N2O. This negative impact will continue out to 2100 if the reductions in these gases are sufficiently large. It can also go beyond this if the absolute reductions continue. For methane, the most significant element in total emissions consists of the fugitive emissions from coal extraction and natural gas extraction, transportation and use, so it is important to cut these as the first priority.

Emissions of methane are currently around 800 million tonnes. Of this total, about 26% can be attributed to coal and gas fugitive emissions (including the failure to manage leaks properly, especially around the year 1990; some mismanagement is still continuing). If coal use were entirely eliminated, natural gas cut down to only 20% of the current use (for non-energy industrial purposes only), “leaks” of natural gas cut to a “normal level”, and emissions from ruminants and rice production continued in line with population, the emissions of methane each year would be about 670 million tonnes. This reduction of 130 million tonnes of methane per year, would represent a negative CO2e, starting at zero for 2030 and growing to 3,250 million tonnes per year by 2050.

Negative CO2e from refrigerant gases

The warming potential from refrigerant gases is expected to decline from 2025, due to the further implementation of the Montreal Protocol. The atmospheric level of these gases should reduce from this date. These gases have about half the impact of methane, so let us say that it also represents a negative CO2e, starting a zero in 2025 and growing to negative 1,600 million tonnes per year year by 2050.

Positive CO2e from Nitrous Oxide

Based on the increase in atmospheric N2O, we can calculate that N2O emissions are running at about 320 million tonnes per year. It may be possible to cut emissions arising from agriculture so that the final number were 160 million tonnes per year. Based on radiative forcing at current levels of emissions, this would mean that the net CO2e from nitrous oxide would be about 1,200 million tonnes.

Positive CO2e from CO2

Based on the foregoing, for a Net Zero outcome, CO2 emissions from all sources would need to be capped at about 4,000 millions tonnes. This compares with the 35,000 million tonnes of CO2 emissions in 2018. This was made up as follows:

  • Coal 13,000 tonnes (including about 2,000 tonnes of metallurgical coal and coal used for residential heating).
  • Oil based fuels 9,000 tonnes.
  • Natural gas 6,000 tonnes.
  • Cement production 1,500 tonnes.
  • Other (undefined) 5,500 tonnes.

Preferably, all coal uses would have to go if Net Zero were to be achieved. All electricity production using natural gas would have to go. All oil-based fuels need to be replaced by chemical alternatives, like ethanol or ammonia, or by electric vehicles. Alternative ways of building heating will be required, using electric air conditioning and heat pumps with local geothermal resources.

Each of these things will be a challenge, but the biggest is the complete change in electricity generation. Under Net Zero, there is no place for natural gas after 2050. At present, renewables like wind and solar cannot supply anything like baseload power, even with all types of storage, so new baseload resources will be needed, such as geothermal and modular molten-salt nuclear reactors.

Electric cars are a bit of dream, at least for nations that are not rich or have large distances to cover. For the latter, something like the ethanol-driven approach of Brazil seems to be required.

There is considerable hope for “green steel” and “green cement”. We wait in anticipation.

Carbon capture, utilisation and storage

This is a major feature of a recent report by the IEA. The question for me is whether it really will be secure at the volumes being considered. They go far beyond current storage being undertaken in depleted oil and gas wells, with the risk of subsequent leakage currently not being seriously considered.

Net Zero in 2050 vs 2060

The foregoing is predicated on achieving Net Zero by 2050. Whether this is a viable strategy for all nations is debatable. A date like 2060 could be more achievable.

For comparison purposes, I have modelled global average temperatures out to 2070, using two targets. One is that Net Zero, according to my definition, will be achieved in 2050; the other is that Net Zero, on the same basis, is achieved in 2060.

Two scenarios for reaching Net Zero.
Two scenarios for reaching Net Zero

This graph shows that a result close to 1.6C can be achieved, even if (my) Net Zero is not achieved until 2060. Of course, it will be a safer outcome if OECD nations can arrive at that point by 2050.

Conclusion

Net Zero by 2050 may be a pipe dream, but the world could give itself a number more years before we reach a stable 1.5C if urgent action were taken. This is because reduced GHG emissions in the intervening years will reduce the growth in average annual global temperatures. This will involve action on the following issues:

  • Do not build any more coal-fired electricity generators where there are other options available.
  • Do not use gas-fired generators for anything except for the purpose of meeting peak demand.
  • Develop geothermal resources where available, and enter into fixed price contracts for the supply of electricity from such resources 24/7 (to ensure that such facilities are not bankrupted by operations that can only provide intermittent supplies.)
  • Governments to push ahead with funding trials for modular molten-salt nuclear-powered electricity generators.
  • Governments to immediately mandate fuel-flex vehicle electronics, so that ethanol can progressively take over as ethanol production increases and where electric vehicles are not suitable for the particular application, or are too expensive.
  • Governments to mandate that ships entering their ports use non-CO2 fuels.
  • Progressively implement reduced N2O agricultural practices as and when the research indicates that this is possible.
  • Governments to mandate that gas not to be used for building heating in new-builds. When electric air-conditioning is not effective in cold climates, governments to mandate that heat pumps using local geothermal methods be used instead.

Remove Greenhouse Gas Emissions

It is feasible to remove greenhouse gas emissions in order to cap global warming at around 1.5C. There are simple and well researched ways to do this. Some are under way but they need more work. Ethanol has been overlooked as a serious strategy. It is argued that all of these ways to cut the emissions of greenhouse gases should be done.

Three approaches are considered here and the likely outcomes predicted based on mathematical modelling of the last 170 years and then predicting out to 2070. This requires estimating the likely greenhouse gas levels at the end of each year.

The ideal case, at least as presented here, is a scenario in which it is predicted that it is possible to hold the increase in global average temperature to 1.5C, stabilising at that level. This requires all nations to participate while holding to the timeline indicated below.

While all nations should not find the actions presented here to be an insurmountable challenge, some non-OEDC nations could consider that the timeline for action will be too difficult for them. To cover this situation, a second scenario is canvassed. In this scenario the timeline for implementation for non-OEDC nations starts in 2050 and goes out to 2070. Under this scenario, the predicted outcome is an increase in global average temperature of 1.7C, stabilising at that level.

Finally, we consider a third scenario, which is the continuation of greenhouse gas emissions at the current level out to 2070. The predicted outcome is an increase in global average temperature of 2C and a steady and unrelenting increase in global temperature after that date.

It is noted that these predictions depend upon not encountering a “black-swan” event (being something not already seen in the last 170 years) over the period of the predictions.

Strategies in the “Ideal Model”

Remove coal by 2050

The removal of coal from electricity generation is already happening in OEDC nations. For modelling purposes, it is assumed that this will be completed for all nations by 2050.

Electricity

Removing coal from electricity generation is the most developed strategy for reducing greenhouse gas emissions, at least in OECD countries.

  • Wind and solar are currently the favoured options in most nations. However since they do not always provide dispatchable electricity, methods of storing electricity and then dispatching it to users are required. Presently, the options available to “store” electricity are pumped-hydro, liquid air and batteries. Liquid-air and batteries can provide a useful mechanism to handle the daily fluctuations in supply and demand; pumped-hydro can handle longer-term fluctuations in supply and demand.
  • Hydro facilities can provide electricity each day as required. Very large facilities can help to manage longer-term fluctuations in supply.
  • Nuclear energy and geothermal energy can provide electricity each day as required.

All storage methods share a single limitation: each can only provide dispatchable electricity if it has previously been stored. In the case of unexpected demand beyond the capacity of renewable resources plus storage to meet, either in the short term or more significantly in the medium term, they do not provide a fall-back facility. Nuclear and geothermal energy are the only currently available fossil-fuel free options that can fill the gap (if they too have capacity). Concerns relating to the safety of nuclear energy may possibly be eliminated by using relatively small molten-salt reactors. If fossil-fuel is to be rejected as a source for electricity generation, this matter should be seriously considered.

Steel

Using hydrogen gas as a substitute for metallurgical coal is being actively explored in several countries. In implementing this, the cost of producing hydrogen gas could be an issue.

Other approaches are already being tried, as discussed here.

Remove 90% of oil-based fuels used for all vehicles and ships by 2050

Action on parts of this plan can be commenced immediately. For modelling purposes, it has been assumed that implementation will begin in 2025 and finish in 2050.

Cars

It is physically and economically feasible to replace all petrol and diesel driven vehicles with ethanol driven vehicles by 2050. It is recognised that, with the falling price of oil, there will be a comparative-cost penalty that cannot be allowed to derail the implementation.

  • Producing ethanol from crops such as sugar cane and corn, while relatively competitive, demands too much land to be a complete solution. Less land-intensive approaches are required. Ethanol from algae has been explored, but it is not yet viable. A viable method of obtaining ethanol from bamboo has been explored. It is accepted that more research is required to develop a solution that will enable the transition to 100% ethanol. (It could be easier to do this than to produce and store hydrogen.)
  • An ethanol-based vehicle fleet has already been established in Brazil. This nation has implemented technology that will allow petrol vehicles to accept any ethanol mixture, from 100% down to 0%.
  • To implement an ethanol-based strategy, all new vehicles must be equipped with this technology. Governments could consider a small government subsidy to make this cost-free to users.
  • Install refuelling bowsers committed to provide a variable ethanol mixture until 100% ethanol supply is sufficiently secure. Variable mixtures to be provided until around 2050.
  • Ethanol to be produced in countries with surplus agricultural capacity. Growing crops in regions that do not require irrigation must be a priority, for example, growing sugar-cane in tropical and sub-tropic regions, preferably delivered via locally-owned and managed ethanol facilities in the countries in these regions. This approach will provide those countries with a way of relatively pain-free economic development.
  • Limit the amount of ethanol required for this change by preferencing plug-in-free ethanol/electric hybrids instead of pure ethanol vehicles.

Trucks

Research in the USA has shown that large trucks can be designed and built to run on ethanol. Change over to this type of engine can be done by 2050. This will require the following steps:

  • Build the engines.
  • Ensure sufficient ethanol supply available to reliably provide all ethanol-driven trucks with fuel.
  • Provide refuelling bowsers that can provide 100% ethanol.

Ships

Research has yet to be done on the best way to convert ships to run on ethanol, but it is assumed that this can done.

Fully-electric vehicles

Fully-electric vehicles are increasingly popular in Western countries. Yet it is difficult to see them as a global replacement for petrol and diesel fuelled vehicles:

  • The demand for electricity from this approach will require a much larger electricity-generating sector. This will be difficult for countries that are already electricity poor, especially in the absence of relatively cheap coal-fired generators.
  • The demand for finite resources in order to build fully-electric cars will create supply difficulties, with the world possibly coming close to exhausting such resources. The supply of cobalt is already under stress and alternatives are being developed. The future supply of copper and lithium could also be a limiting factor.
  • Fully-electric cars at present are much more expensive that plug-in-free hybrids. While this cost differential should reduce over time as a result of manufacturing efficiencies, it also likely that supply problems could cause the opposite outcome.

Remove oil-based fuels for aeroplanes by 2070.

At present, hydrogen for aeroplanes is just an idea, although widely canvassed. For modelling purposes, it is assumed that it will begin in 2050 and be completed by 2070.

It is now recognised that it is unlikely that batteries will be a viable fuel source for long-distance aeroplanes. Currently attention is being given to using a hydrogen-based fuel. This will require three things:

  • A more cost effective way of producing hydrogen gas is required (possibly from water through electricity).
  • A cost effective way of compressing hydrogen gas is required.
  • The proposed aviation fuel is to be proven to be reliable.

It is assumed that this can be done by 2070.

Remove 90% of natural gas from electricity generation by 2050

Natural gas is currently considered the cheapest and most effective way to provide peaking electrical energy. Removing natural gas from the equation will require the implementation of similar strategies to those required for the removal of coal from the electricity-generation process.

Reducing the use of natural gas will have an another benefit: reduced fugitive gas emissions will progressively cut the level of methane in the atmosphere.

This change is unlikely to happen until 2040 and could be completed by 2050.

10% of natural gas has been retained in the model to allow for additional peaking capacity to be retained in the system to cover the times the electricity grid is under unexpected demand stress.

Remove 90% of natural gas from building heating and industry by 2070.

Natural gas provides a versatile fuel for heating. It works in all climates and is relatively non-polluting. The remaining problems are the CO2 generated from burning it and the methane lost during the processes of extraction, transportation and use. The following strategies could be implemented to remove this fuel use:

  • Increase the volume of methane trapped from organic waste.
  • If a cost efficient way of producing hydrogen gas from water through electricity is developed, it can be used for heating.
  • Electrically driven heat pumps can be used for heating provided an appropriate system is chosen and it is shown to be cost effective.

It is assumed that these strategies can begin to be put in place by 2050 and be fully implemented by 2070.

Cut CO2 emissions from the manufacture of cement by 2070.

  • Methods to be developed so that CO2 from cement manufacture can be eliminated.

Other Actions

These are things that are being done in some places and should be done everywhere straightaway.

Ideal Outcome

If the above strategies to remove greenhouse gas emissions were adopted by all countries, the predicted result is that global average temperatures increases since Industrialisation will be held to 1.5C by 2050 and beyond, with a standard error of ± 0.11 (mostly due to El Niño and La Niña changes in some years and volcanic eruptions).

The modelled values are based on a calculated formula that takes into account the forcing from the additional greenhouse gases in each year and deducts the estimated cooling effect of atmospheric sulphur. More details on the formula can be obtained here.

In this model, no allowance has been made for capture of CO2 and its storage underground. This could be considered, as a last resort, by nations unable to follow this “Ideal Model.”

Split Model

The Split Model covers the situation of the OECD nations following the “Ideal Model,” but the other nations deferring taking these drastic action to remove greenhouse gas emissions until between 2050 and 2070. In this case, the predicted result is that global average temperatures increases since Industrialisation will be be 1.7C, with a standard error of ± 0.11 (mostly from other cyclic climate factors).

Stable Case

The starting point for the Stable Case is the assumption that emissions will continue out to 2070 at the 2018 levels of emissions. It therefore is called the “Stable Case.” (It is assumed that, in the period to 2030, reductions in CO2 emissions after 2018 in OECD nations will be offset by “catch-up” emissions in the other nations.) The stabilising of globalised CO2 emissions was the substantive result of COP21 Paris.

We can expect a temperature increase of around 2C by 2070 if the world follows the Stable Case, with further increases after that date.

Modified IEA-based model

An IEA report, Energy Technology Perspectives, designed to model the actions required to cut greenhouse gas emissions, assumed that significant real CO2 emissions will continue well past 2070. Therefore, carbon capture, utilisation and storage was an important part of its predicted “net zero” outcome. Since most of its predicted actions can be envisaged as taking place towards 2070, it is likely that a stabilised temperature increase of around 2C will be the result of its strategies, around the outcome of the Stable Case for 2070, but with no further temperature increases.

However, using the IEA report framework, it remains possible to consider cutting CO2 emissions substantially by 2050 even without carbon capture and storage.

A “Modified IEA-based model” of this kind would deliver a global temperature increase of 1.6C, being a result somewhere between the other two main models. The downsides of this approach is that it demands virtually immediate action and some very costly infrastructure. It is unlikely that either of these elements will be delivered. On this basis, the “Ideal model” is to be preferred: it offers a better outcome as well as implementation being less costly and less disruptive.

Comparing temperature outcomes

Different outcomes using different removal strategies.
Projections of Global Average Temperatures

Conclusion

While all the actions to remove greenhouse gas emissions described here are important, there are two actions that will make the biggest difference to the final temperature outcomes.

  1. Removing fossil fuels from electricity generation, especially coal, but also natural gas. Both have a very significant impact on the final result and both create CO2 and methane emissions.
  2. The immediate adoption of a strategy to convert all vehicles from fossil fuels to ethanol. This will be simpler, quicker, cheaper and less resource depleting than the currently favoured electric car strategy.

In addition, many small actions to remove greenhouse gas emissions will accumulate to have an appreciable impact on the final result.