237

Survey on Household Wood Biomass Use and Energy Consumption
in the Oku-Aizu Region
Shogo NAKAMURA* and Takuya TOGAWA
Fukushima Branch, National Institute for Environmental Studies
10-2 Fukasaku, Miharu Town, Tamura-gun, Fukushima, 963-7700, Japan*E-mail: nakamura.shogo@nies.go.jp

Abstract
We surveyed and analyzed the current status of household energy consumption and use of firewood andother wood biomass in the town of Mishima, Fukushima Prefecture for the purpose of building a supply chain
model for forest resource use in mountainous regions. The number of questionnaires returned was 341, with a
response rate of 48.6%. The survey results revealed that approximately 9% of households were using woodbiomass combustion devices. Annual firewood consumption per household was 3 m3, and over 90% of the
raw logs used were procured inside the town. The difference in the ages of the houses of firewood users andnon-users suggests that building structure may have influenced this result.
Key words :	firewood, household energy consumption, mountainous area, questionnaire survey, wood stoves

1. Introduction
Ascertaining the status of wood biomass utilization
for household wood stoves and other wood-burning isimportant from the perspective of utilizing regional forest
resources and tackling climate change. Although cold
mountainous regions tend to be sparsely populated, percapita energy consumption for heating is likely to be highand, therefore, deserves detailed investigation.
Several studies have already been conducted on theuse of wood biomass from the viewpoint of solving
environmental problems simultaneously. Nemoto et al.
(2017a, b) investigated household use of wood biomass
combustion devices from a nationwide view. Regionally,
Hatanaka et al. (2011, 2012) surveyed household use ofwood-burning devices in 10 municipalities in Nagano
Prefecture from the viewpoint of effects of carbon
emissions reductions. From the viewpoint of promoting
usage of unused biomass, Ogasawara et al. (2017)
investigated the use of firewood in fruit-producing areas
and found higher use of wood stoves and other woodburning devices than in other areas owing to the readyavailability of tree prunings. Many case studies at a local
scale have also been conducted, for example, Izumi et al.
(2018) conducted a random electoral-register-based
sampling survey to ascertain the level of firewood use in
Shiwa Town, Iwate Prefecture. Harashima et al. (2014)
researched the utilization of wood stoves and other woodburning devices and firewood consumption in the
Minowa district of Ina, Nagano Prefecture, through avisual survey and questionnaire. Uezono (2018) also
Global Environmental Research
24/2020: 237-242
printed in Japan

conducted a questionnaire survey on household energy
consumption in both mountainous and urban areas of theSan’in region in western Honshu. These studies indicatedthat currently the consumption of firewood is stable inboth mountainous and urban areas, but the amount offirewood consumption is very limited compared to therich potential of this resource from domestic forests. The
role of woody biomass energy should be reconsidered
compared to other energy (electricity, gas, and so on)
based on reliable field surveys with promotion to asuitable environmental policies such as transformation toa decarbonized society.
With regard to energy consumption in theresidential sector, the Ministry of Internal Affairs andCommunications’ Family Income and Expenditure
Survey (2018) includes data on household expenditures
for electricity, kerosene, gas and other energy sources
broken down by city classification, drawn from a subsetof the survey sample. Data on household energy
consumption by city classification nationwide are alsoavailable in the form of estimates for the residential
sector in the Agency for Natural Resources and Energy’s
Energy Consumption Statistics by Prefecture (2018) andthe Ministry of the Environment’s Statistical Survey ofResidential Sector CO2 Emissions (2018).
Few studies, however, have looked specifically at
the level of wood biomass use in relation to household
consumption of various energy resources in mountainous
regions. The town in Fukushima Prefecture that was
selected as our studied area decided to promote usage ofwoody biomass and started to survey the current situation©2020 AIRES

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S. NAKAMURA et al.

of forest and biomass consumption inside and near the
town. In this study, in collaboration with the town, we
conducted a questionnaire survey of all households in a
mountainous district to shed light on the trends andcharacteristics of household energy consumption and useof wood biomass, which is a forest resource. This study
provided the town the basic information on instituting
environmental policy regarding woody biomass asenergy.

2. Survey and Analysis Methods
2.1. Study Area
The mountainous location chosen for this study was
the town of Mishima in the Oku-Aizu region of
Fukushima Prefecture (Fig. 2 in Ooba et al., 2020). The
Oku-Aizu region is colder than Aizuwakamatsu Cityand other locations at the same latitude, with mean
temperatures approaching those of northern Tohoku, thenorthernmost region of Japan’s main island of Honshu.
Depending on the year or month, Oku-Aizu can receive
more than double the snowfall of Aizuwakamatsu.
Mishima is a small municipality with a populationof about 1,600 people living in approximately
750 households scattered among 18 villages. Its elderly
ratio (percentage of the population aged 65 or older) is
54.1% (Fukushima Prefecture, 2020). At its peak during
the development of the Tadami River hydroelectric dam,Mishima’s population topped 7,700; since then, however,the population has steadily declined, prompting the town
to launch various initiatives to attract young residents
from other parts of Japan and otherwise curb
depopulation. Given that it has a forest coverage of 88%(Forestry Agency, 2018), the town is also considering
measures for exploiting its forest resources, including theTable 1 Items surveyed in the questionnaire.
Category

Item

House

Type of house, building structure, age, total floor area,
number of buildings, number of rooms, owned/rented,
renovation/rebuild history, building structure at rebuilding

Number ofheatingdevices

Kerosene stove/kerosene fan heater,electric stove/oil heater, gas stove, heated floor, kotatsu,
air conditioner

Households
that usefirewood

Number of devices, annual firewood consumption,
procurement method, purchase price, source,
raw wood production location, intention to continue
using equipment, problems, reasons for quitting,desired support measures

Households
Type of equipment, reason for quitting, conditions forthat stopped
using firewood again
using firewood
Energyconsumption
statusMonthly electricity, kerosene, and LPG costs, electricity
billing plan, installed energy-saving equipment, numberof people at home during the day (weekdays, holidays)

Attributes

Family age/gender composition, occupation, residential
district name, confirmation of respondent’s family
relationshipuse of wood biomass energy in public facilities andsubsidies for using firewood.
2.2 Survey Method
We conducted a questionnaire survey of 702
households, representing all of the households in
Mishima except occupants of homes for elderly people
requiring special care. The survey was conducted from
October 20 to November 6, 2017, with questionnaires
being distributed to each household by the town throughward chiefs and returned by postal service. The numberof questionnaires returned was 341, with a response rateof 48.6%.
The questionnaire, which was to be filled in by thehead of each household, asked about type of house, useof heating equipment, use of wood biomass combustion
devices, consumption of electricity, kerosene, and othersources of energy, and household attributes. Table 1
shows the items surveyed in the questionnaire. We went
through these by hand, and based on the questionnaire
responses, identified the characteristics of households
using wood biomass combustion devices and comparedthem with households not using such devices.
For converting the amount of firewood used into3
wood biomass consumption, we assumed that 1 m offirewood = 800 kg and that one bundle = 13 kg.

3. Results and Discussion
3.1 Use of Wood Biomass Combustion Devices
Figure 1 shows a breakdown of devices owned byhouseholds using wood biomass. Approximately 9% of
the households were using wood biomass combustion
devices (wood stoves, fireplaces, cookers, boilers) at thetime of the survey. Although this was lower than values
found by previous studies (13.5%: Izumi et al., 2018;27.4%: Yasumura et al., 2011). Wood stoves and boilers(firewood-heated baths etc.) accounted for most of thewood biomass combustion devices being used, with 11%
11%
3%
30%

46%

5%
5%

Wood stove
Fireplace
Other
CompoundCookerBoilerFig. 1 Breakdown of household wood biomass combustion devices.

Survey on Household Wood Biomass Use and Energy Consumption in the Oku-Aizu Regionof firewood-using households using more than one typeof device.
The number of years since households started using
firewood combustion devices varied from several decades
to several years prior; of these households, 28% started
using these devices in 2010 or later. Looking at therelationship with house renovation/rebuilding and woodbiomass utilization, although 17% of firewood-using
households installed devices when renovating or
rebuilding, no such relationship was observed in mosthouseholds. Among households not currently using woodbiomass, approximately 19% of all respondents indicatedthat they intended to use firewood combustion devices in
the future subject to availability of cheap firewood andsubsidies for installing devices. This indicates that,combined with existing users, a potential 27% ofhouseholds may use firewood combustion devices given
the right conditions.
Most existing users obtained their firewood either byproducing it themselves or procuring it for free fromacquaintances rather than purchasing it from vendors.
Over 90% of the raw logs used were procured in Mishima
Town, either from the users’ own forest plots or from theplots of acquaintances.
3.2 Number of Heating Devices
Table 2 shows heating device ownership ofhouseholds in Mishima Town. The percentage ofhouseholds equipped with air conditioners was relatively
low in Mishima, with most households using kerosene
stoves and fan heaters for heating purposes. A comparisonof the number of other heating devices owned by users

239

and non-users of wood stoves and fireplaces shows thatusers of firewood for heating purposes owned fewer
kerosene stoves and fan heaters than non-users. However,ownership of other heating devices such as kotatsu orheated floors was higher among firewood users than nonusers, albeit only slightly. Among households using woodstoves, all but one household owned only one stove. Thissuggests that almost all of the households using woodbiomass also used fossil fuels or grid electricity forheating purposes. The percentage of household energy
consumption used for heating is a matter for future
investigation. The sample size of firewood users for thisquestion was small, and statistical tests found no
significant differences in mean values.
3.3 Household Energy Expenditure
Table 3 shows the mean household energy
expenditure in Mishima and other locations in Japan’s
Tohoku region in 2017. Energy expenditure in Mishima
was high compared with mean values in the Tohoku
region, indicating high energy consumption for heating
purposes. Kerosene and electricity consumption tended to
be lower among firewood-using households (Table 4),
while consumption of LPG (Liquid Petroleum Gas) was
almost double compared to the amount consumed by nonusers. These differences, however, were not found to bestatistically significant (t-test, p<0.05), and a moredetailed statistical analysis would be needed such as
factor analysis (covariance structure analysis or statisticalcausal analysis) according to the building age of thehouse related to the performance of thermal insulation.

Table 2 Heating device ownership and mean number of devices owned.
Device type

Ownership as a percentage of
all households (%)

Mean number of devices owned
by firewood users

Mean number of devices owned
by firewood non-users

Kerosene stove/fan heater

93.8

2.23

3.10

Kotatsu

80.4

1.31

1.08

Air conditioner

42.2

0.62

0.75

Electric stove/oil heater

26.4

0.15

0.39

Heated floor

6.2

0.08

0.07

Wood stove

3.5

1.08

-*

Gas stove

1.8

0.00

0.03

*This question was not asked of firewood non-users

Table 3 Mean annual household energy expenditure (unit: JPY/year)
Electricity

Mains gas

LPG

Kerosene

Mishima Town

130,656-

65,41858,585

Fukushima City*

127,437

19,08833,38925,386Morioka City*

100,629

18,24837,17731,723

Tohoku region*

114,770

15,51636,026

40,113* Source: Family Income and Expenditure Survey 2016 (Ministry ofInternal Affairs and Communications, 2018)

Table 4 Firewood use and energy costs (JPY).
Energy (per month) Firewood use Number
Kerosene
LPG
Electricity

MeanStandard deviation

User

13

9,700 (94.8%)

16,000Non-user278

10,000 (100%)

9,900

User

11

8,900 (172%)

15,000Non-user254

5,200 (100%)

5,400

User

13

9,800 (89.7%)

5,300

Non-user306

11,000 (100%)

9,300

240

S. NAKAMURA et al.

3.4 Wood Biomass Consumption and Substitution
EffectAnnual firewood consumption per household was
3
3 m . Assuming this firewood was used in wood stoves,
the amount of heat generated by burning this amount is
6.55 GJ, which is equivalent to 208 L of kerosene or
31.5% of mean annual household kerosene consumption(660 L) in Mishima. In terms of costs, almost all firewoodin Mishima was either self-procured by felling trees or
obtaining logs for free from acquaintances. Only one
household surveyed purchased firewood, but at theextremely low price of JPY 200/m3. Assuming that the
firewood used in Mishima households lowered kerosene
use by 208 L at the prevailing price of JPY 89/L and thatno costs were incurred in firewood procurement, use of
firewood reduced annual household heating costs byapproximately JPY 18,500.
3.5 Wood Biomass Use and Energy Expenditure
We conducted independent sample t-tests to compareenergy expenditure for kerosene, LPG, and electricity
between firewood-using households and non-using
households (Table 4). Although mean energy expenditure
between the two groups differed, this difference was notstatistically significant. The lack of differences may be
due to other factors such as the small sample size,
differences in usage of heating and hot water supply, ordifferences in household attributes.
3.6 Wood Biomass Use and Household Characteristics
To investigate the reasons for no statisticallysignificant difference being found between the energy
costs of firewood-using households and non-using
households, we conducted independent sample t-tests on
the difference in means with building age, floor area,
number of buildings, number of rooms, renovation/
rebuilding history of the households surveyed as separate
dependent variables and use/non-use of firewood as theindependent variable. The homes of firewood-using
households tended to be older (Table 5).
As shown in Fig. 2, we also compared the number ofpeople per household. Only mean building age wasfound to differ between firewood-using and non-using
households at the p <0.05 level (Table 5), with the homesof firewood-using households tending to be older.
Owing to poor insulation and other factors related tohouse structure in firewood-using households, energy
expenditure would likely be even higher than inTable 5 Use/non-use of firewood and household attributes
Firewood use

NumberMeanStandard deviation

Building age(years)

User

12

110

69

Non-user

303

71

55

Floor area
(m2 )

User

13

190

210

Non-user

328

160

179

Number of rooms
Persons per household

Number of hea�ng devices owned

Persons at home during the day(weekdays)

User

12

7.8

3.7

Non-user

314

7.5

2.8

User

12

2.8

1.9

Non-user

293

2.4

1.5

User

12

1.8

0.75

Non-user

299

1.6

0.97

120
100

User

Non-user

80
60
40
20
0

1
No
response

2

3

4

5

6

7

8

9

10

Persons per household

Fig. 2 Persons per household in relation to number of heating devices owned for use/non-use of firewood.

Survey on Household Wood Biomass Use and Energy Consumption in the Oku-Aizu Region
Kerosene cost
(JPY/month)
Firewood use
User
Non-user

LPG cost (JPY/month)Fig. 3 Use/non-use of firewood and energy expenditure
per month.
Kerosene cost per month(during usage period)

241households procuring their own firewood for free. Annual
firewood consumption per household was 3 m3, assuming
this firewood was used in wood stoves, the amount ofheat generated was equivalent to 31.5% of the meanannual household kerosene consumption in the town.
Usage of firewood is economical, bringing a reduction in
annual household heating costs of approximately JPY
18,500. These findings showed firewood still to be major
heat resource in this town, and this trend is the same as
was seen in previous studies (e.g., Izumi et al., 2018).
Total demand for firewood inside the town can be selfsupplied from the forest resources (Ooba et al., 2020).
In 2019, Mishima Town installed a new air
conditioner system using fire-wood boilers in one of thetown’s public facilities, Seikatsu Kogei-Kan (Mishima
Local Crafts Museum), referring to our policy suggestion
based on this study and other studies conducted byour project team (e.g., Ooba et al., 2020). This boiler
system was coupled with the startup of a new small-scale
firewood supply chain inside the town. Local companies
in the town with the potential to provide more firewood
intend to expand the biomass supply (personalcommunications). In the future, suppliers need to bematched with consumers of firewood at the local scale.
Additionally, to transform this heat resource froma depletable to a renewable energy to achieve a
decarbonized town, more detailed field surveys andanalyses of related policies for not only biomass but also
house building and renovation should be conducted.
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Fig. 4. Energy expenditure in relation to building structure.

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Figure 3 shows the relationship between firewood
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use, the relationship between building structure andfirewood use shown in Fig. 4 indicates that firewood use
may be effective in reducing energy consumption inwooden houses, which require higher energy
consumption.

4. Conclusions
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Shogo NAKAMURA
Shogo Nakamura is a researcher in the Regional
Environmental Renovation Section of the
National Institute for Environmental Studies,
Fukushima Branch. He holds a Ph.D. inagricultural science. He has played a central rolein developing the energy monitoring systems in
Shinchi as well as many other areas in
Fukushima. Recently his interests have led him to participate in theEnvironment-Economy-Society Integration Research program.

Takuya TOGAWA
Takuya Togawa is a senior researcher at the
National Institute for Environmental Studies,
Fukushima Branch. He received his doctorate inengineering from the Graduate School ofEnvironmental Studies, Nagoya University in2010. He is engaged in research on mechanisms
for realizing disaster recovery and regional
revitalization by effectively utilizing local environmental resources.
(Received 21 December 2020, Accepted 28 December 2020)