The pros and cons of harvesting trees to generate electricity were highlighted in three Island Voices essays published last month in the Honolulu Star-Advertiser.

One, on Feb. 1, argued that tree preservation is needed to fight climate change and that tree-fueled generation projects should not be approved (“Burn some biomass to generate electricity — but not trees”).

On Feb. 7, a similar point was made about proposed legislation to “meet Hawaii’s net-zero emission goal” (“Bills on ‘firm’ and ‘renewable’ energy undermine environment”).

A third piece, on Feb 14, pointed out that projects, specifically the Honua Ola bioenergy project on Hawaii island, that grow fast-growing species for the purpose of generation can be carbon negative (“With Honua Ola Bioenergy, there will be more forests, trees”). You simply plant before you harvest and harvest only what you have grown, always staying ahead in the sequestration-minus-emissions calculus.

As different as these strategies sound, they both fail to sequester carbon in the long run. As a mature forest approaches its maximum biomass, it releases about as much carbon from decay as it sequesters. Similarly, as the strategy of grow-harvest-and-burn continues, the rate of sequestration approaches zero.

A better way to sequester carbon, create economic value and still support bioenergy is to use tree trunks for wood products, and to use the residues from logging and milling for generation. Using the wood as building material, furniture and other wood products stores the carbon for long periods such that new carbon “banked” in each cycle of harvest, produce, and burn-the-waste can be much greater than the bioenergy emissions plus the depreciation of wood products.

In this way, the “bank account” of sequestered carbon can be increased indefinitely, especially for fast-growing species that warrant a faster optimal rotation period, e.g., eight to 10 years. This provides a win-win solution for the economy and the environment. In contrast, neither the preserve nor the plant-and-burn strategy can sustain a substantial rate of sequestration.

These comments ignore the amenity values and ecological services (e.g., recharging groundwater aquifers) that forests provide and do not therefore justify clearcutting existing forests, even for replanting purposes. Rather, the focus should be on afforestation, especially of fallow or marginal lands. Some minimum project size is also required, at least enough to justify the initial costs of setting up a local wood industry. The challenge now is demonstrating the social profitability of local wood production, including the value of carbon sequestration, which may warrant a modest subsidy.

Nor should Hawaii’s “100% renewable” law be used as a justification for burning the entire tree. The renewable electricity law, originally House Bill 623, does not mandate (as widely reported) that 100% of the state’s electricity be generated from renewable energy resources no later than 2045. Rather, it requires that renewable generation, including rooftop solar, divided by a utility’s net sales, be at least 100%. That fraction ranges from zero to infinity and can be greater than 100% with less than 50% of consumption coming from customers’ own renewable generation and with 50% of a utility’s own generation coming from fossil fuels.

The law also includes a list of 12 loopholes (including a lapsing of tax credits or a demonstration of excessive economic harm), any one of which can be used as justification for not meeting the standard. Rather, energy and forest policy should be crafted according to the Hawaii Constitution, which calls for promoting the general welfare as well as environmental stewardship.

James Roumasset is professor emeritus in the economics department at the University of Hawaii-Manoa and research fellow at UHERO (University of Hawaii Economic Research Organization).