Our Green Down Payment:

Fighting Climate Change by Turning Buildings into Carbon Sinks with Timber Bamboo

This article is an adapted summary by Tobe Sheldon, and any errors are hers alone; you can read the full white paper by Hal Hinkle, Ph.D., here.

Humanity faces a climate precipice. Unless we significantly slow the course of climate change through emission reduction and the removal of existing atmospheric carbon. Yet, carbon removal options are limited, primarily unproven, and costly to operate. Growing wood forests to maturity is an option for carbon removal, but harvested wood is a hot commodity. And, trees take many decades to accumulate their carbon removal. Plus, once harvested, only about 50% of the tree-captured carbon becomes storable in a building, compared to nearly 70% for timber bamboo. Another critical advantage of timber bamboo is that it can be harvested annually, starting around year seven (after first planting) and then annually after that, making it five to six times more carbon productive than wood.

Moreover, timber bamboo is four times more efficient in total fiber production for the same planted land area. So, suppose we accelerate our adoption of timber bamboo into the built environment, that would mean we could build four houses compared to one from the same planted area. And, we can turn buildings into carbon sinks and make a crucial “green down payment” on the carbon removal needed in the current decisive decade.

Code Red For Humanity

There is no escape from the ominous evidence of accelerating climate change seen in extreme weather events’ increasing frequency and devastation. July 2021 was the hottest month globally ever recorded. The scientific and policy climate communities focused on 2050 and 2100 as key horizons only a few years back. Now, President Biden and many others are calling 2030 “the decisive decade for climate action,” and the UN Secretary-General just issued a “code red for humanity” warning. The scientific opinion is unanimous: we must reduce greenhouse gas (GHG) emissions and remove existing GHG from the atmosphere. This urgent push for change is necessary because the earth’s climate system is comprised of multiple powerful tipping points, which once triggered can’t be righted again and only accelerate the crisis.

We have limited options to remove carbon from the atmosphere.

Most of us know a wide range of ways we can reduce emissions. But the methods to remove emissions already in the atmosphere are less familiar. Conceptually, we have maybe six broad options. The most expensive of which are enhanced weathering, bioenergy with carbon capture and sequestration, and direct air capture with sequestration. These geotechnical solutions are far more speculative, less immediately scalable, and cost multiples more per ton when and if they can begin to scale than natural climate options.

The chart below from a 2018 article by a global group of nineteen independent scientists summarizes six major carbon removal options (A to F). Each option is assumed to have reached its maximum scaling. Thus, the cost (or profit) to remove a ton of carbon dioxide is on the vertical axis. The theoretical amount of carbon dioxide removed (in gigatons/year) is on the horizontal axis.

Notice that all six options A to F fall below the cost-profit breakeven line, meaning they will cost money to remove GHGs. The upper three of these six options, afforestation and reforestation, agricultural soil carbon sequestration, and biochar ©, are “natural climate solutions.” You will notice that afforestation and reforestation fall above and below the profit line. That is because the original graph did not account for sustainably harvesting trees for durable wood products. This means forestation can be profitable to remove carbon from the atmosphere. Wood products can store captured carbon in buildings and keep it out of the atmosphere for many generations. When you add the harvested wood products to the equation, you can pay for the cost of forestation with the profits. This multiplies the amount of carbon removal forestation we can afford because it is profit-making in the ordinary course of human economic activity.

Planting trees is good, but…

Realistically, even with harvested wood products, wood forestation can’t remove sufficient atmospheric carbon fast enough. This is because (most) trees don’t grow fast enough to help slow climate change in the critical short term. Trees accumulate their carbon over many decades. In the early years, growth for most tree species is relatively small compared to growth after the first two decades. The time window for humankind to rely principally on forestation to help address our decisive decade is closing fast. We need a fast-growing plant that can capture GHG, sequester carbon, and be harvested for profitable products.

And this is where our hero enters the story…

Timber bamboo is a giant grass that grows to its full height in its first year. Final height can range from 60 to over 100 feet when growing from a mature stand, four to seven years after the initial planting. Fortunately, like trees, timber bamboo can also be harvested and turned into durable building products that store the captured carbon. But, as a grass, timber bamboo grows new culms (stalks) from the underground root system that can be harvested annually by intercutting (never clear-cutting). This annual regeneration cycle allows timber bamboo to constantly capture carbon and produce durable harvested wood products every year, starting around year seven. Timber bamboo grows prolifically in the tropical and subtropical areas of the Americas’, Asia, and Africa. Globally, timber bamboo covers about 1% of the land area that tree forests cover.

We studied the overall carbon flux of timber bamboo compared to commonly used North American framing timber using the United States Forestry Services data. The results were surprising. As the chart below illustrates, in the crucial first 20 years, timber bamboo captured carbon over 400% better than wood. However, when studied for a more extended 75-year period, timber bamboo and its resultant harvested building products outperform wood by 500% to 600%, depending on assumptions used.

Also, in terms of land-use intensity, timber bamboo is over four times more efficient than trees. This is because of bamboo’s faster growth and the annual harvesting cycle compared to wood’s slower growth and 25–75 year harvesting cycle. For example, producing vertical framing timber for a single prototype house each year requires 1.25 hectares of wood versus .27 hectares of timber bamboo.

Timber bamboo has a stronger strength-to-weight ratio than concrete or steel.

Structurally, while wood is optimally effective in the low-rise building sector, it can’t quickly displace high carbon footprint concrete and steel dominating the mid and high-rise markets, which is where significant growth will occur in the next three decades throughout the developing world. Concrete and steel generate more than 10% of global GHG emissions. And despite many efforts to lower the carbon intensity of concrete and steel, there are high theoretical limitations to the likely improvements to the carbon footprint of concrete and steel. Fortunately, timber bamboo mechanical properties typically exceed wood by 25% to 100% for the same volume or density, as illustrated below. Some engineers even refer to timber bamboo as vegetal steel. Thus, incorporating timber bamboo alone or in conjunction with wood is a vital tool to help decarbonize mid and high-rise buildings.

Reclaiming marginal lands while carbon farming…

Timber bamboo can be grown on marginal lands, prevent soil erosion, and intercut annually. Because the bamboo doesn’t die when harvested, a harvest emission event doesn't release decades of stored carbon. Instead, the rest of the bamboo clump keeps growing and putting up new shoots. Effectively, we can use timber bamboo to farm carbon perennially and store the carbon in buildings.

Globally, the area of deforested or already disturbed land ranges from 350 to 1780 million hectares. More specifically, 500 million hectares of this degraded land are in the tropics and subtropics, a prime growing area for timber bamboo. In the theoretical case that just the degraded tropical areas are planted with timber bamboo, our estimated total carbon removal is over 130 gigatons in 20 years, about three years of total global emissions. Even a fraction of this would be a crucial green down payment as we explore and develop the less-proven carbon removal options.

Given the speed of growth, profit opportunity, land-use efficiency, and strength advantages, timber bamboo is uniquely positioned to help humanity remove carbon from the atmosphere in the immediate future. We accept that all the options in the carbon removal portfolio are essential to explore in the long run. But we can’t get to the long run unless we can navigate around the approaching climate tipping points. This means our focus must not be just on the tantalizing high-technology, geoengineering solutions but also the immediate and profitable solution of timber bamboo.

This article is a summary of “Our Green Down Payment: Fighting Climate Change by Turning Buildings into Carbon Sinks with Timber Bamboo,” by Hal Hinkle, Ph.D. Any errors in this summary are by Tobe Sheldon. You can read the full white paper here.