Future Fuels in Arboriculture

Northern Tree Service has chosen to fuel its fleet (April through October) using B20 biodiesel, reducing the company fleet’s carbon emissions by more than 500 tons per year, an achievement viewed favorably by its clients. Photo courtesy of Northern Tree Service.

The Intergovernmental Panel on Climate Change (IPCC) has made it clear in their 2022 reporting that, while we are approaching a tipping point (+1.5ºC) for climate change, there is still time to avert the most damaging climatic impacts. Many believe this need to be acute, necessitating immediate reductions in greenhouse gas emissions, most notably carbon dioxide (CO2) and methane (CH4). This article will explain what avenues one tree care company explored to reduce its carbon footprint, but first we need to get a little science and other background out of the way.

While complicated, this science can be summarized by recognizing that since industrialization, humans have utilized increasing amounts of fossil fuels. Accessing this energy has released its sequestered carbon (1 gallon diesel = 22.5 pounds CO2) into the atmosphere, where it traps heat and warms the planet. While exactly how much use of fossil fuels affects climate change compared to natural or other factors may be debated by some, it is generally accepted that their use is a significant contributing factor.

In response to a desire to decarbonize, many governmental organizations have established programs loosely analogous to regressive taxes. In these programs, load-servicing entities – power or fuel suppliers – are statutorily obliged to purchase a percentage of their deliverables in the form of energy attribute certificates (EACs), which facilitate energy produced by renewable sources. This concept may seem remote to many until they realize that the 10% ethanol-gasoline blend is the manifestation of the federal Renewable Fuels Standard (RFS). This legislation was established during George W. Bush’s administration to both support farmers and reduce dependence on (imported) fossil fuels.

In alignment with the federal RFS legislation, many individual states have adopted similar portfolio standards, which are intended to facilitate green power generation (solar, batteries, combined heat and power, hydro, etc.).

Since 1997, Massachusetts has led the nation with decarbonization programs, offering incentives for green power, heating and energy storage. While these programs have proven successful in establishing a vibrant renewable industry sector, it has come at a cost. Massachusetts ratepayers have some of the highest power bills in the continental United States.

One company’s effort to reduce emissions

Northern Tree Service is a third-generation arboricultural company located in central Massachusetts that is proud of its unparalleled track record of innovation. Therefore, in an effort to better meet the expectations of its New England clients, Northern has chosen to lead by example and reduce its carbon footprint. As a large arboricultural contractor with a weekly diesel consumption of approximately 7,500 gallons, an obvious green initiative for the company was to change how its fleet was fueled. In doing so, Northern Tree Service has explored three pathways, each with its own advantages and challenges.

Electric power

Recognizing the increasing popularity of heat pumps and e-vehicles, Northern engaged its long-time partner, Altec, to explore what it would take to build an electrified bucket truck (70-foot stick). After a deep dive into the feasibility of this project, including conversations with several truck manufacturers, it became clear that the chassis development has not progressed sufficiently to support the battery bank necessary for a 10-hour workday, including 100 miles of driving, all on a single charge. This constraint is amplified by cost projections proposed by chassis manufacturers. However, during Northern’s engagement, it was learned that a proof-of-concept vehicle had been built. Unfortunately, the vehicle’s performance and cost made it clear that further development was needed.

It is worth noting that while e-vehicles produce no local emissions, they are still charged from the electric grid. In New England, the electric grid is supplied by a generation infrastructure that is far from green. At the time of writing this article, the electricity needed to fuel the author’s laptop was only 8% renewable (which includes waste-to-energy generation). Investment in industrial-scale green generation must parallel e-vehicle adoption for the system to be truly renewable. The author recommends interested readers download the free “ISO to Go” application to their smart phones, as it provides unparalleled, real-time, easy-to-understand information on New England’s energy profile.

Renewable natural gas

Vanguard Renewables farm-powered anaerobic digester at Goodrich Farm in Salisbury, Vermont, converts food and farm waste into renewable natural gas. Photo courtesy of www.vanguardrenewables.com.

Following a disappointing investigation into e-vehicles, Northern Tree Service turned its attention to renewable natural gas (RNG), also referred to as sustainable natural gas (SNG). Simply put, this fuel is naturally occurring methane that has been refined to meet pipeline-quality standards (wild type CH4 processed and compressed into a liquid). Importantly, this refinement allows it to be fully interchangeable with conventional natural gas, a fuel that currently propels many municipal vehicles. Any vehicle equipped with a natural-gas engine can be fueled with RNG.

This screenshot shows the sources providing energy to the New England power grid at any moment. Only 8% was from renewables in this view from April 12, 2022. Graphic courtesy of ISO to Go app/ISO New England, Inc.

However, despite excellent potential and 100% renewability, this solution also hit a dead end. Finding access to liquefied, renewable natural gas is virtually impossible.

Despite a clear lack of availability, it is worth noting that capturing methane for use as RNG from landfills, agricultural biodigesters or wastewater treatment facilities is extremely virtuous. Methane, which is the unavoidable product of anaerobic (low- or no-oxygen) decomposition, has been shown to be 25 to 80 times more damaging as a greenhouse gas than carbon dioxide. It is, therefore, meritorious that industries dealing with liquefied waste (confinement agriculture and wastewater treatment facilities) are supported in their efforts to capture methane for processing into a virtuous RNG fuel.


Finding insurmountable hurdles with electric and RNG fuels, Northern Tree Service found success with biodiesel. This naturally liquid, 100%-renewable fuel, often referred to as B100 or neat biodiesel, is created by refining waste products like used cooking oils, tallow, yellow grease and various vegetable derivatives. While somewhat new to the marketplace (with the associated variability in standards), biodiesel can be used in existing fleets.

Biodiesel is seldom blended at levels higher than B20 (20% bio and 80% fossil). Graphic courtesy of www.staroilco.net.

However, because biodiesel is approximately 30 times more hydroscopic than conventional diesel, it is markedly corrosive, necessitating stainless-steel tanks, fuel lines and unique injectors for unblended use. A further complication for application in cold climates is that biodiesel is also more prone to gelling. For these reasons, biodiesel is seldom blended at levels higher than B20 (20% bio and 80% fossil).

Nevertheless, in the spirit of innovation, Northern Tree Service has chosen to fuel its fleet (April through October) using B20, at least until electric or RNG options are more feasible. Despite offsetting only 20% of its fuel (when seasonally possible), the choice to use biodiesel has reduced Northern Tree Service’s fleet carbon emissions by more than 500 tons per year, an achievement viewed favorably by all of Northern’s clients.

In alignment with cultural expectations to combat climate change, it is likely that the tree care industry can expect increasing client pressure to reduce its carbon footprint. While employing electric chain saws and blowers may be both virtuous and effective for optics, the associated decarbonization is simply out of scale with the industry’s vehicular emissions. This pressure will likely spur further innovation, advancing the development of other transportation technologies.

* Renewable identification numbers (RINs) are credits the U.S. Environmental Protection Agency (EPA) uses to track and enforce compliance within the Renewable Fuel Standard.

Jonathan T. Parrott, Ph.D., is a Massachusetts licensed forester, ISA Certified Arborist, Certified Treecare Safety Professional and director of safety, education and special projects with Northern Tree Service, Inc., a 45-year TCIA member company based in Palmer, Massachusetts.

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