Nature Knows Best - Carbon Farming

For the past 20 years, since Ed Mazria calculated that buildings use almost 50% of energy consumed in this country, I have been on a quest to make buildings super energy efficient, while producing any additional energy needed from site-generated renewables. But now I am coming to believe that there is another option for reducing greenhouse gases that is equally, if not more, important.

A carbon experiment on a small number of ranches in Northern California is establishing a simple, benign way to remove carbon dioxide from the air. UC Berkeley scientists have measured the impact of a one-time spreading of compost ( ½ “ layer) on rangeland and found, to their surprise, that it boosted the soil’s carbon sequestration capacity on average one ton per hectare per year for each of the 8 years they have been testing. They forecast that this sequestration process will continue for at least two decades.

Grazing is the largest land use on the planet and most grazing lands are degraded. If this one-time thin application of compost were applied to a quarter of California’s rangeland, the soil would absorb ¾ of California’s greenhouse gas emissions for the year, and since the effect is cumulative, it would keep doing so for a number of years.

For centuries humans have been bleeding soil-stored carbon into the atmosphere through plowing, overgrazing and poor agricultural practices. These recent compost applications can reverse this and create what scientists call a positive feedback loop. Plants pull carbon dioxide from the air through photosynthesis and transfer a portion of the carbon to the soil through their roots and soil microorganisms, then turn that carbon into a form commonly known as humus. This process improves soil fertility, boosts plant growth and captures even more carbon, while enhancing the soil’s ability to absorb and retain water.

Where is all this compost going to come from and who is going to pay to have ranchers spread it on their land? The compost has to come primarily from cities. San Francisco composts 700 tons of residential and commercial organic waste everyday—the largest such operation in the world. This can become a great resource for ranches. As for compensation, key efforts are being made to incorporate soil carbon offsets in California’s cap-and-trade system as a way to make it profitable for ranchers to restore their land.

Although only recently recognized as a carbon sequestration strategy, “carbon farming” has already captured the attention of the White House and officials as far away as Brazil and China. This inexpensive, low-tech harnessing of natural systems holds the potential to turn the vast rangelands of California and the world into a weapon to reverse climate change.

What Makes a Home "Green"?

Multi-year drought, distressed forests and intense wildfires bring awareness of the local impacts of climate change. Efforts to address climate change have long focused on cutting greenhouse gas (GHG) emissions and more recently on sequestering carbon. But because the impacts of climate change are now upon us, we need to add to our efforts resilience planning. What is the focus of these efforts related to our buildings?

In reviewing many “green building” programs, the most common characteristics are: energy efficiency, water conservation and selecting materials that are sustainable and used in a resource-efficient way.

Because energy use is strongly linked to GHG emissions, reducing energy consumption in homes tends to decrease damage caused by burning fossil fuels. There are many ways to reduce energy use in homes: install more efficient appliances, select higher performance windows, or add thicker insulation.

Water conservation makes sense in most regions of the country, excluding only those where fresh water is abundant. In California, water is directly linked to energy, for close to 20 percent of our energy use statewide is consumed in transporting and treating water. Residential water conservation emphasizes careful selection of plumbing fixtures and appliances but also promotes rainwater collection.

Choosing materials for a green home involves selecting materials that are naturally renewable (for example, wood from sustainably harvested forests), have recycled content, or are harvested/manufactured regionally. These materials also need to be incorporated in structures as efficiently as possible.

Other green building criteria worth considering are:

·         Designing and building homes that last longer. Although rarely thought about, designing to make future changes easier helps save materials. Selecting materials that require less cleaning and less maintenance are also aspects of durability.

·         A green home is small. Scaling down is unpopular with Americans, but greatly reduces impact.

·         A green home provides superior indoor air quality and promotes human health. Avoiding materials and furnishings that involve toxins and outgassing is key. Good natural and mechanical ventilating is also important.

·         Because transportation involves our biggest consumption of fossil fuel, selecting a location that is close to work, shopping, schools and public transportation could be the most impactful of all criteria, but is rarely addressed.

Resilience focuses on livable conditions in buildings after a disaster; on backup power; and on access to potable water. These strategies are being woven into “green building” programs but expanded to community scale. Photovoltaics with on-site storage can provide basic services and information during power outages. We know how to build tight buildings out of non-combustible materials to resist wildfires. Mechanical ventilation with HEPA (high efficiency particulate air) filters can handle smoke and ash from wildfires. Rainwater collection, composting toilets and recycled water are other resilient strategies.

Choosing the Right Building Materials for a Low-Carbon Future

Many have advocated for tight houses with low energy needs and highly efficient mechanical systems as one of the best ways to address climate change. California now requires all new houses to be zero-net-energy, although natural gas is still allowed. A new study by Chris Maywood, director of the Endeavour Sustainable Building School in Ontario, Canada, questions this singular focus on cutting building energy use. His research concludes that curbing the emissions resulting from the harvesting, manufacture and transport of building materials, what he calls a building’s up-front embodied carbon emissions (UEC), is significantly more important than the contribution from running a building on clean, renewable energy.

Zero-net-energy makes a big impact on carbon emissions, but most of that impact is in future years as a result of on-going zero energy consumption in the building’s operation. On the other hand, if UEC is zero or even provides net carbon storage, the impact on climate is immediate and powerful. Emissions that are avoided today do more to slow climate change than emissions that are averted in the future.

What materials make the difference between a high UEC structure and one that stores carbon? A high carbon house would use such common construction materials as standard concrete, extruded polystyrene insulation, brick cladding, steel frame-vinyl windows, tile and carpet flooring and concrete or clay tile roofing.

A carbon storing building would utilize concrete where much of the Portland cement has been replaced by fly ash or other substitute materials. It would be insulated with cellulose and wood fiberboard. Sustainably grown wood would be used for the framing, for wood flooring, for wall paneling and for wood windows. Linoleum might also be on the floors. Sun baked Mexican clay tiles (low embodied energy) would be a good roofing choice for our high-fire area. The study recommends plant-based building materials such as straw panels, hemp fiber board, and rice straw medium-density fiberboard, because they prevent the release of stored carbon for the life of the building.

Because the report only focused on materials that are available, code-compliant and affordable, architects and builders can make major carbon reductions with only minor adjustments to what we already do. The optimum, obviously, is to create carbon storing buildings that also run on renewable energy.

The conclusions in this report are a major revelation to the building industry. The analysis relates only to new construction, but the same team is undertaking a new study covering retrofits. Maywood’s hunch is that there will be even bigger climate-impact opportunities with remodels.

Retrofitting Homes to Become All-Electric

Weaning homes off natural gas and other fossil fuels would significantly reduce carbon emissions. Scientists report that fossil fuels consumed in our buildings across the globe account for 28 percent of climate change, while natural gas leaks upstream from our appliances account for another 25 percent of global climate change. Fuel burning appliances are entrenched in our homes, making the shift to electric appliances a challenge, even to homeowners so inclined.

The City of Santa Barbara is finalizing an all-electric code for new construction, joining more than 40 other cities and counties in California. Most likely, Santa Barbara and Ventura counties will consider similar code changes soon, but what can be done about existing structures, nearly all of which are not all-electric?

Redwood Energy, a California energy consulting firm, has published, within the last few weeks, a peer-reviewed report laying out detailed information on how the conversion of an existing home can be simple, relatively inexpensive and without building modification, not even upgrading the electrical service. This report, A Pocket Guide to All-Electric Retrofits of Single-Family Homes, lays out two paths toward electrification.

One path is an appliance-by-appliance conversion. This incremental approach, where an electric equivalent model replaces a gas-burning appliance may have no cost difference, especially if the old appliance needs replacing anyway. If a new 240-volt circuit is needed, there would be an added cost of between $85 and $600.

The second path is where all appliances are replaced at one time. This can cost between $3000 and $20,000 or more, depending on whether building upgrades are included like adding insulation or new high-performance windows.

Most existing homes have a 100-amp service panel; a few older ones may have only a 60-amp panel. The report lays out how a 3000 square foot home can be completely electrified without upgrading a 100-amp service. Choosing efficient appliances such as heat-pumps that are three to five times more efficient makes this possible. Switching to water heating or space heating/cooling heat-pumps usually means running new 240-volt lines but appearing on the market for the first time this past year are 120-volt models than can plug into any wall outlet.

Another strategy is using circuit-sharing plugs where one 240-volt outlet can handle, for example, an electric dryer and a heat-pump water heater, or a magnetic induction stove and an electric vehicle charger. These circuit-sharing plugs range between $200-$500 but save money by requiring fewer new circuits and often no panel upgrade.

Redwood Energy’s report is full of useful information on design, assessing existing electric panels, rebates and tax credits, plus utility and community choice energy incentives (coming to Santa Barbara this October). It contains an extensive catalog of devices that covers everything from heating and cooling to cooking, water heating, whole-house ventilation, countertop ovens, kitchen hoods, power-sharing plugs, and even slow cookers.