Research Trends and Results

Using the energy of plant waste from cities
YAMAGISHI Yutaka, Senior Researcher
SONE Naoyuki, ResearcherKURIHARA Masao, HeadLandscape and Ecology Division, Road Department(Key words) Biomass, plant waste, energy use, storage
1. Introduction
One low carbon city creation policy is the use ofpruned branches and mowed grass etc. from greenparks and roadside trees, etc. (below called, “plantwaste from cities”) as sources of energy. However,while plant waste from cities has been chipped for use
as fertilizer or materials as part of green recycling, it
has rarely been used to supply energy. In response tothese background circumstances, the Landscape andEcology Division has been conducting “research onthe use of local production for local consumption typereusable energy in cities” since FY2012. This reportintroduces the potentiality of the use of plant wastefrom cities as an energy source based on the results ofthese researches.
2. Plant waste from cities
According to “Concerning the Present State andRoadmap for Biomass Utilization Technology” in the“Biomass Commercialization Strategy” prepared inSeptember 2012 by the Biomass Utilization PromotionCommittee concerning the use of this energy, its
practical use is possible now (2012) and in about 5years (about 2017), and that source materials will
include woody material and grassy plants.
Standards for the use of woody biomass as fuelinclude the Proposed Guideline to Fuel Use Chip
Quality Standards of Iwate Prefecture, which is a local
government that makes advanced use of woody
biomass, Wooden Chip Quality Standards of theNational Wood Chip Industry Federation, and thewood pellet quality standards enacted by the Japan
Wood Pellet Association in harmony with the EN
Standards for Non-industrial Use Wooden Pellets
enacted jointly by 28 countries of Europe in 2010.
Comparing the characteristics of plant waste from
cities as a fuel with these standards shows that
immediately after pruning and mowing, the moisture
content of the pruned branches and mowed grass ishigh. And measurements of the ash content of theleaves of the pruned trees and of the mowed grassshow that it is higher than the standard levels, and thatthe contents of sulfur (S), nitrogen (N), and chlorine(Cl) are also higher than the standard values.

3. Future development and use of the results
Presumably pruned branches without leaves contain alot of tree bark, but it is believed that it will bepossible to use energy just like normal wood. So a
study is being made of a process in which immediately
after branches are pruned, their moisture content islowered to prevent decay or fermentation, then they
are stored and later used as energy.
And trial calculations of the quantity produced in
two districts in Japan are being done, including, notonly plant waste produced in cities by the maintenanceof public works such as rivers, roads, parks, etc., butalso other woody biomass such as construction waste,
and surplus forest material. (See the figure).
And present technology studies concerning thepossibility of using energy of small-scale parks etc.
dispersed plant waste from cities, and including theresults of the above study, will be summarized in thedocument, Technology Document Concerning
Methods of Using Energy of Plant Waste from Cities
that will be released as a TECHNICAL NOTE ofNILIM.

Photo. Use of Branches Pruned from Park Trees to Heat
Park Facilities(Oi Pier Central Seashore Park: Tokyo)(Left: Chip dryer using solar heat, right: boiler)

Figure Quantity of Usable Wooden Biomass around
Showa Memorial Park (Trial Calculation)