Agriculture Reference
In-Depth Information
M
ETHODOLOGY
Data collection from field interviews and focus
group discussions
Interviews and focus group discussions with stakeholders, farmers and
potential customers used a partially pre-coded questionnaire to elicit WTP
and determine attributes of farmers' perception and farming practices.
Additional data were collected from government institutions, IWMI urban
and peri-urban agriculture (UPA) library, Ghana o
ce of the Food and
Agriculture Organisation of the United Nations (FAO), Ghana Organic
Agriculture Network (GOAN) library and farmer associations. A total of 200
individual interviews were conducted with farmers from different urban
farming systems in and around Kumasi. Few women were involved in
agriculture in Kumasi; therefore, specific attempts were made to interview as
many women as possible to elicit their opinions. The contingent valuation
method (CVM) was used during interviews with farmers to estimate the price
they would pay for compost based on their knowledge of similar products
such as poultry manure or black soil. The CVM approach involved surveying
individuals to determine whether and how much they are willing to pay for
compost under different hypothetical scenarios (Whittington et al, 1990;
Asenso-Okyere et al, 1997; Alberni and Cooper, 2000). Farmers were asked
whether they were willing to pay for compost as a soil improver and how
much they were willing to pay for a 50-kg bag. A bidding game was
introduced in situations where farmers found it dicult to understand and
provide their bids. This bidding game helped to determine the zero WTP, and
the mean and maximum amount the farmers would pay for the compost
(Field, 1994; Hanley et al, 1997; Akpalu, 2000; Nugent, 2001).
Further questions focused on socio-economic characteristics, income,
experience with compost and perception of compost quality. Since the
dependent variable was a dichotomy (yes - 1 or no - 0), it was deemed
appropriate to use a probit model instead of traditional regression models.
The probit model was used to explain the factors that could affect farmers'
WTP for compost (Kennedy, 1990) (Table 2.1). The probit model is defined
as:
Pr
ð
y
¼
1
j
x
Þ¼
ð
xb
Þ
where is the standard cumulative normal probability distribution and xb is
the probit score and takes care of the explanatory variables (Pindyck and
Rubinfeld, 1983). The parameters in the probit model were estimated by
maximum likelihood methods (Pindyck and Rubinfeld, 1983; Hailu, 1990).
Compost production and analysis
The compost plant produced four types of compost with differing ratios of
household waste, market waste and dewatered fecal sludge. The first compost
