THE EDGE

New geosynthetics design online tool for unpaved roads

Roads built over weak soils reduce allowable truck payloads, inhibit vehicle traction, pose a safety hazard, and lead to higher road maintenance costs over time. Critically weak road sections also reduce transportation efficiency, thus limiting access to fibre.

To address this challenge, FPInnovations has just released an online tool for its members, FPGeoDesign, that is based on FPInnovations’ previously published Geosynthetics Design Guide: Reinforcement Solutions for Unpaved Roads.

FPGeoDesign is used to determine the required thickness of compacted aggregate when geosynthetic reinforcement is used, and to make a comparative analysis between a reinforced section and an unreinforced section. The nature and properties of the subgrade soil and aggregate base course materials, as well as the expected traffic, are the main inputs to the tool. Different geosynthetic reinforcement options can be compared amongst each through simplified cost analyses. Several types of geosynthetics can be compared side by side.

For more information, please contact Francis Bober, Researcher, Transportation and Infrastructure at FPInnovations.

How to access FPGeoDesign (FPInnovations’ members only)

1. Send a request by email to Giuseppe Costanzo at [email protected].
2. On your mobile device, install the Microsoft Authenticator app for Android (Google Play) or for iPhone (App Store), which is used to verify your online identity quickly and securely. The app is mandatory to access FPGeoDesign.
3. You will soon receive an email from Giuseppe Costanzo asking you to accept an invitation to access an FPInnovations application. This email is legitimate and is part of the registration process to access the FPInnovations member portal.
4. Once your registration is completed, go to https://fpgeodesign.fpinnovations.ca/
   and log in with multi-factor authentication using Microsoft authenticator.

Practical measuring and monitoring of high yield afforestation for natural climate solution opportunities

By Tony Kryzanowski

Trees can be part of a natural climate change solution because of their ability to sequester a substantial amount of carbon. But the question is how to determine and validate exactly how much carbon individual trees and plantations sequester.

The Canadian Wood Fibre Centre (CWFC) of Natural Resources Canada in co-operation with soil scientists at the Canadian Forest Service present this handy reference guide to calculate carbon sequestration on both an individual tree and area basis.

For individual trees, it is first important to calculate the stem tree volume. Take a diameter measurement at 1.3 metres up the stem, diameter breast height (DBH), followed by a measurement of total tree height. These measures should then be applied to a known formula for a specific species to calculate a total above ground stem volume measurement in cubic metres. An algorithm is then applied to the stem volume to incorporate below ground stump and root volume (~35 to 42 per cent) and tops and branches (~30 to 37 per cent) to deliver a total cubic metre measurement.

Next, this measurement is applied against the mean dry weight of the tree based on sample analysis of local trees or averages by species. For example, the dry weight of hybrid poplar according to samples analyzed by CWFC for Prairie-suitable hybrid poplar clones is .382 grams per cubic centimetre, or 382 kilograms per cubic metre.

Using hybrid poplar again as an example, that cubic metre with a density of 382 kilograms of dry weight per cubic metre yields approximately 45 to 50 per cent carbon. The yield depends on the hybrid poplar clone or tree species (most common species in Canada are in this range), site location and climate. By applying the kilogram density per cubic metre against the carbon units of approximately 45 per cent, it is possible to calculate the kilograms per cubic metre of actual carbon.

It is now important to convert the amount of sequestered carbon into carbon dioxide equivalent because it is an escalating greenhouse gas of concern. That is achieved by multiplying calculated carbon mass content in the individual tree by 3.667, a factor related to the molecular weight of CO2. Carbon has an atomic mass of 12 and oxygen has an atomic mass of 16, totaling 44 for CO2. This equates to 3.667 kilograms of CO2 per kilogram of carbon.

Therefore, the formula to convert the mass of a hybrid poplar to its potential for carbon and carbon dioxide sequestration is volume in cubic metres multiplied by dry weight in kilograms multiplied by 45 per cent and then multiplied by 3.667. Using one cubic metre of stem volume as an example, applying the calculations in the previous paragraphs to hybrid poplar equates to ~1 tonne of CO2.

As a reference, the CWFC has determined that one tonne of sequestered carbon dioxide is equivalent to a 27 centimetre DBH hybrid poplar measuring 27 metres tall.

“We have created a reference sheet that shows diameters, heights and stems per hectare and how that translates to total carbon tonnes sequestered per hectare,” says Derek Sidders, Program Manager, Technology Transfer and Development at CWFC.

To calculate the amount of sequestered carbon within an area, let’s consider a plot of a certain dimension within a hectare, which is 10,000 square metres or 2.471 acres. CWFC’s sample plots are typically clusters of 100 square metre circular plots with a radius of 5.64 metres. Considered as a percentage of a full hectare, it is possible to calculate total carbon and carbon dioxide equivalent in tonnes per hectare.

Now it is important to consider growth rate which represents incremental carbon sequestration potential per year. For a typical moderate to high intensity managed hybrid poplar afforestation plantation, the growth rate is 12 to 20 cubic metres of growth per hectare per year over the tree’s lifespan at 100 per cent stocking.

“Afforestation plantations mature usually in sixteen to twenty-five years and so it is possible to accrue anywhere from 12 to 22 carbon dioxide tonnes per hectare per year,” says Sidders, “which is a significant value when applied at the present $30 per tonne of carbon dioxide equivalent, and shortly, $50 per tonne.”

He adds that by using this simple method, it is possible for landowners and investors to track carbon stocks or to understand total carbon dioxide sequestration potential of individual trees, taking the whole tree above and below ground into consideration.

In addition to functioning as an excellent medium for carbon sequestration, afforested or reforested trees obviously have additional value at maturity for solid wood products, bioenergy, or a variety of bioproducts as opposed to releasing the carbon into the atmosphere through onsite burning or natural decay.

** The calculations above represent a case scenario for Canadian Prairie-suitable hybrid poplar and are an indication of the maximum or gross units produced by these plantations in all woody parts of the trees. Fractionate the trees by component (stem, tops and branches, stump and roots), to get an estimate of the relative units associated with each.

For more information about this afforestation carbon dioxide sequestration measuring and monitoring method, contact Derek Sidders at [email protected].