Climate Solutions: Reaching Net Zero Emissions

Climate Solutions: Reaching Net Zero Emissions

By Wahhab Baldwin

March 2020

We know from the IPCC reports that the world needs to reach net zero greenhouse gas (GHG) emissions within 30 years. But what would that look like? Is it even possible for us to completely stop emitting greenhouse gasses?

I didn’t even know the answer to that question when I started this series, despite having read fairly widely on the climate crisis. But I have become convinced that it is not unrealistic to reduce our GHG almost to zero — say by 95% or more — within that timeframe, and that is without including carbon capture and sequestration (which may be needed in time, since we ultimately need to have negative emissions). This article is an overview of what that would look like for the United States.

To start, we need to understand what our sources of GHG emissions are now. The Environmental Protection Agency lists the following sources:

However, Land Use and Forestry serves as an offset, or sink, for greenhouse gasses, absorbing about 11% of the above emissions.

It’s not my intention here to go through the process of moving from where we are to where we need to be. Some of my other articles do go through that. California has been leading the way, and by studying them and successful European countries, we have plenty of good data on steps that work. Instead, let’s just jump ahead to 2050 and see what our nation looks like.

Electricity production can be replaced by a combination of wind and solar power, in addition to our current hydropower and nuclear. Nuclear currently accounts for nearly 20% of our electricity generation, and although many ecologically oriented people are opposed to nuclear energy, we don’t have time to replace it as well as the 64% of our electricity currently generated by fossil fuels. Germany phased out nuclear in reaction to the Fukushima accident, and deadly emissions spiked. On the other hand, even though new-generation nuclear power plants are much safer, produce less waste, and have other advantages over our aging light-water reactors, it is most likely both too expensive and too time-consuming to add new nuclear.

Because both wind and solar are intermittent sources, some form of energy storage will need to be used so that we can make full use of the energy produced at times of peak wind and sun, and have access to that energy when it’s dark and windless. While there are some forms of storage under development or in use, I believe the two primary forms in 2050 will be batteries and generating hydrogen. Currently, battery storage is quite expensive, but the price is dropping rapidly and will do so further as industrial-scale storage is more widely used. Hydrogen generation will be of great importance for industry but can also fuel generators[1] to act as “peaker plants” when more electricity is needed than is being produced.

It will be necessary to upgrade our electrical grid, both to reduce line losses and to make excess electricity from one area available in another. Use of micro-grids, including input from buildings with rooftop solar, will also make our overall grid more effective.

With zero-carbon electricity, dealing with transportation is not too hard. Thirty years gives plenty of time to replace our existing fleet of gasoline and diesel powered automobiles, busses and trucks with electric or fuel cell vehicles. Of the 29% of our GHG emissions that transportation represents, 82% represents light-Duty Vehicles and medium- and heavy-duty trucks. 9% of that 29%, or about 2.6% of our total, is aircraft, and while we may be able to make aircraft more efficient, we may not have carbon-free aircraft by 2050. As for trains and heavy ships, which account for about 1.3% of our grand total, I do not know if they can be made completely carbon-free, but they can certainly be made significantly more efficient, and simply eliminating hauling oil and coal will reduce their use.

Industry’s emissions come from burning fossil fuels for heat, as in making steel, from chemical reactions, as in making cement, from leaks from natural gas and petroleum system, and from use of petrochemicals (as in making plastics). Burning fuels for heat is over half of the total, and recent work both with solar arrays as well as small, modular nuclear reactors can be used to provide industrial levels of heat where needed. As the cost of carbon goes up, though taxes or otherwise, industry will learn to be more effective through eliminating leaks, recycling, including making use of waste heat, and choosing different chemical processes. For example, cement is responsible for 6% of global CO2 emissions. Cement manufacturers are already starting to produce lower-emitting cement and there is even discussion of making cement carbon-negative or replacing it. Dealing with plastics is challenging, and will need to be dealt with by a combination of methods.

Commercial and residential buildings reductions can be brought about by converting heating and cooking to electric, and through more efficient design for new buildings and retrofitting old ones. One source of emissions in this category is methane produced by landfills; the technology for capturing and producing energy from this methane already exists.

Agriculture produces GHG primarily from excess nitrogen generating N₂O (nitrous oxide), from cattle and other livestock producing methane, and from manure management. While we can reduce growing beef cattle by taxing it and providing delicious substitutes, some percentage of these emissions is probably irreducible.

So that’s it! Those are all the emissions we need to eliminate. We have seen that we already have the technology to reduce or eliminate all of them. There may be around 9% that cannot practically be eliminated. However, we still have the arena of Land Use and Forestry, which serves as a net sink of greenhouse gasses. According to the Environmental Protection Agency, “In the United States overall, since 1990, Land Use, Land-Use Change, and Forestry (LULUCF) activities have resulted in more removal of CO₂ from the atmosphere than emissions. Because of this, the LULUCF sector in the United States is considered a net sink, rather than a source, of CO₂ over this time-period.” Currently, this offsets about 11% of total U.S. greenhouse gas emissions. However, we can increase this number. Key methods are planting more trees, regenerative agriculture, and improving grazing management practices on grassland.

One hundred eighty years ago, there was a boom in sheep in New England — an estimated 4 million of them. By 1850 it is estimated that only 25% of New England was still forested. But when sheep farming stopped being widespread, the forest regrew. Today, New England is about 80% forested. So it is possible to recover. It is possible to be a carbon sink rather than a carbon emitter. We know how to do it. We simply need to act.