Subtask 1.3 Photo Essay

Production of high quality feedstocks through comminution

Waste to Wisdom conducted one of several experiments to produce high quality feedstock through comminution (chipping and grinding) in September 2014. This experiment studied how different types of residual woody biomass material behaved when processed with a commercial chipper. The goal was to produce high quality biomass material, or feedstock, that is consistent in size and low in contamination (bark and dirt).

In addition, the study focused on producing quality feedstock that’s suitable for use with biomass conversion technologies such as gasification, pyrolysis, and densification. These technologies turn woody biomass into a more energy dense material.

* Biomass + gasification = biochar
* Biomass + pyrolysis + pelletization = torrefied pellets
* Biomass + densification = briquettes

Five different material types were produced for the study: processed (delimbed stem wood only) hardwood and softwood tree tops, unprocessed (limbs and needles still intact) hardwood and softwood tree tops , and slash (chunks, limbs, and needles). The output from each material type was evaluated for particle-size distribution, bulk density, moisture content, and ash content.

Humboldt State University led the experiment along with several project partners — Oregon State University College of Forestry, Peterson Pacific Corporation, Steve Morris Logging, and Green Diamond Resource Company.

(Click on the upper left image below to go to slideshow view with full captions for each image.)

In an earlier experiment — Subtask 2.1: Sorting and arranging forest residues — softwood and hardwood trees were harvested and the residual woody biomass left after processing sawlogs — tree tops, limbs, and chunks — had been sorted into five feedstock types that underwent varying degrees of processing. Sorting the biomass into feedstock types is different from traditional logging operations in that this slash was specifically sorted and arranged to facilitate a follow-up biomass operation. Remember that most forest residues are regarded as waste and burned in the forest, not processed and converted as occurred in this study. Photo: Joel Bisson, Humboldt State University

In the Subtask 2.1 experiment, tops where separated from slash material. The tops were then piled into different test configurations — tipis, criss-cross, processor piled, and scattered on the forest floor — in order to study the best ways to 1) minimize contamination, 2) facilitate grinding and chipping, 3) improve moisture content control, and 4) improve handling and transportation efficiency. A criss-cross pile is shown. Photo: Tom Waddell, Forest Business Network

Which raises the question — why is the study so concerned about lowering the moisture content of the residual biomass? Processing bioenergy or bio-products is less efficient when moisture content is higher. This is true for biochar and torrefaction. And briquetting moist material does not result in a brick that holds together well. Therefore, briquetting is intolerant of moisture content. Finding the best ways to pile biomass in the woods and letting it air dry lowers the moisture content, which improves the quality to aid in more efficient processing, and also lowers transportation costs. Photo: Tom Waddell, Forest Business Network

The team setup shop at a centralized worksite on Green Diamond Resources land in northern California where they experimented with feeding the various types of feedstock through chipping and grinding equipment. Photo: Craig Rawlings, Forest Business Network

Modified dump trucks were loaded with biomass piled at various sawlog processing sites (landings), which then hauled the different feedstocks to the centralized landing site. The trucks were modified by extending the sides and tailgate in order to carry more payload. Photo: Christopher Lanning, Forest Concepts

First to be tested were the processed conifer tree tops through the chipper. Photo: Tom Waddell, Forest Business Network

The loader equipped with a log grapple, then fed the unprocessed conifer tops into the chipper. Photo: Tom Waddell, Forest Business Network

The final test was the slash, which was sent through a grinder. Photo: Craig Rawlings, Forest Business Network

Humboldt State University researchers — Joel Bisson, Anil Raj Kizha., and Han Sup-Han — bagged chip and grind samples for analysis at the lab. The researchers will study the bulk density, ash content, and size distributions of the different raw materials after the chipping or grinding. Photo: Tom Waddell, Forest Business Network