Do Renewables Have a Carbon Footprint?

Earlier this year, the director and filmmaker Michael Moore released a documentary titled "Planet of the Humans." Through various interviews with people involved in the renewable energy industry, the film claims that the carbon footprint of the most common renewable energy technologies such as solar, wind, and especially biomass burning is comparable to that of fossil fuel sources of energy. While the film received a tremendous amount of criticism, it did raise several valid questions. This line of thought is often avoided by people involved in the renewable energy movement.

Much research has shown that the life-cycle greenhouse gas emissions of renewable energy sources are generally lower than fossil fuels. However, unlimited demand for any energy will inevitably cause problems to surface. For example, lithium mining to power millions of home batteries and electric cars connected to rooftop solar panels comes with enormous environmental costs. The documentary mentioned above, despite some rather outlandish claims, did its job. It forced its viewers to grapple with the need for restraint and limitation in our demand for energy sources, even if they are renewable.

What Promise and Challenges Does the Hydrogen Economy Pose?

In 2003, author and economist Jeremy Rifkin wrote a book titled "The Hydrogen Economic: The Creation of the Worldwide Energy Web and the Redistribution of Power on Earth." The thesis or conclusions of the book were just as hopeful as its title suggests. Essentially, Rifkin argued that a peaceful transition away from the fossil fuel era would be made possible by a new, democratic, and environmentally friendly energy regime. He envisioned a future world where abundantly available hydrogen fuel cells would be democratically available to people worldwide, thus powering our society without contributing to global warming. Hydrogen, abundantly available in the Universe, was called by Rifkin "the forever fuel that never runs out and produces no harmful CO2 emissions."

Fast forward twenty years or so, and many of Rifkin's predictions have failed to surface. As of 2019, however, hydrogen fuel cells were being used in certain automobiles. The Toyota Mirai, Hyundai Nexo, and Honda Clarity are a few of the hydrogen fuel cell vehicles that are commercially available. Their main by-product is water (instead of carbon dioxide).

Unfortunately, there are still several barriers to the widespread adoption of hydrogen as a source of low carbon energy for different uses. While hydrogen is one of Earth's most abundant elements, it doesn't exist alone but rather in combination with other elements, like water.

The process of separating hydrogen atoms from water for use as a low carbon fuel was mainly completed using a process known as steam methane reforming (SMR). Unfortunately, this process relies on substantial energy inputs and produces large amounts of carbon dioxide as a by-product. Recent estimates find that the SMR process emits an average of 7 kg of carbon dioxide for every 1 kg of hydrogen produced. Globally, the SMR process is responsible for about 3 percent of global carbon dioxide emissions produced by the industrial sector.

In a 2008 technical document, the EPA reported that the US produced about 9 million tons of hydrogen per year. This amount of hydrogen production led to 60 million metric tons of CO2 emissions annually. Emitting almost seven times the amount of carbon dioxide as hydrogen is not feasible if we want to transition to a post-carbon economy. For comparison's sake, the life cycle CO2 emissions for solar panels comes out to about four grams of CO2 for every kWh of renewable energy produced.

When vehicle manufacturers for hydrogen fuel cell cars claim that their electric vehicles emit only water vapor and warm air, they only refer to immediate tail-pipe emissions. A broader view would allow the consumer to discover that the feedstock for the production of hydrogen used in car fuel cells most likely comes with an enormous amount of emissions.

Then, hydrogen as a low carbon, zero-emission fuel source continues to be similar to thermonuclear fusion: a possibility that continues to be technologically unattainable.

What Advances Have Been Made in Hydrogen for Net-Zero Home Heating?

Just because we still haven't found a way to separate hydrogen for use in zero-emission fuel cells efficiently doesn't mean that this potentially abundant energy source should be abandoned. About fifty years ago, the best solar panels could only achieve an efficiency rating of 9 percent - and that was in highly controlled laboratory settings. After years of innovation and research, commercially available solar panels regularly achieve 20 percent efficiency at just a fraction of the price.

Similarly, continued research into hydrogen fuel cells might yield possibilities for lowering the emissions from separating hydrogen and making this fuel alternative more cost-competitive. One of the most exciting areas of current research is related to hydrogen energy for net-zero home heating. Below, we'll briefly explore a few of the recent development in hydrogen for net-zero home heating.

BDR Thermea Group

In the Netherlands, the BDR Thermea Group is a company that manufactures and distributes innovative products and services that save energy and cut carbon emissions. Last year, the company revealed a pilot project that implemented the world's first hydrogen-powered domestic boiler for home heating. One of the most innovative aspects of this pilot project is that the hydrogen fuel was delivered via existing natural gas pipelines. The boiler burns pure hydrogen that was 100 percent sourced from wind or solar energy. This pilot project has proved that existing fossil fuel infrastructure (such as gas pipelines) can be repurposed for future hydrogen heating. It has also shown that carbon-neutral renewable energies, such as wind and solar, can be used for separating hydrogen atoms to be used as a fuel. Hydrogen boilers are still in development. However, over 400 of these boilers are set for distribution in the UK in the coming years. This deployment could potentially make hydrogen boilers a competitive cost source of carbon-free home heating in Europe.