This study aims to evaluate the energy consumption and economic results for sustainable production of Mentha × piperita L. var. officinalis Sole f. rubescens Camus, also known as Mentha Italo Mitcham (Black Mint or English peppermint) [1]. The area of study is the municipality of Pancalieri and its surroundings, in the Northwest of the Piedmont Region, Italy. Mint has been cultivated in the study area since the 18th century, while the Mentha Italo Mitcham (Menta of Pancalieri) species began its cultivation in the early 19th century. In Italy, Piedmont Region is one of the most important for MAP cultivation with 248 farms covering 870 ha (2010) amongst the 2,938 farms and 7,191 ha Italy-wide (2010). Of the Piedmont Region MAP crops, mint is the preeminent species [2,3]. Regional data indicates that mint is of interest to about 40 farms and 100 ha between the exprovinces of Torino and Cuneo [2]. Mint from Pancalieri-known for its superior quality-is used almost entirely (99%) for essential oil production. Pancalieri mint is unusual in that about 80% of it is purchased by a single food producer in the region (2015), making its ‘market’ essentially non-existent. After a brief description of the production process, this work evaluates and discusses energy consumption during the production process, followed by evaluation and discussion of some economic aspects.

The production processes

The mint production process begins in November with soil preparation (ploughing, harrowing) of a field, after which stolons are taken from the field on which they had been cultivated in the previous year and transplanted. Planned weeding occurs during pre-emergence in March, followed by alleyway clean-up in May. Fertilization is in March (2) and September (1), and the first irrigation takes place in May with an additional one in June. Harvest occurs with a single cut in August followed by distillation (whole plant, ‘green herb’). The two to three-year cultural cycle follows a consistent production process throughout the area of study, with slight alterations in fertilization (a single one in spring) or irrigation. Additionally, some farmers recently have substituted the top of the plant to stolon’s in the transplanting.

Energy and economic aspects

Energy consumption: The energy consumed to produce mint was derived from the fuel and lubricant amounts consumed as well as from farm machine manufacturing energy consumption [4]. To calculate actual energy input, we employed several coefficients: machine with engine 92.0 MJ kg^-1, equipment without engine 69.0 MJ kg^-1, fuel 37.0 MJ L^-1, and lubricant 83.7 MJ kg^-1 [5,6]. For the fuel and lubricants, 1.2 MJ kg^-1 was added to account for their distribution [7,8], while 55% of the total energy content in each machine was added for maintenance and repair [9]. The fuel consumption calculation used a ‘topping-off system’, in which the machine tank is re-filled after each work cycle [6]. Finally, lubricant consumption was estimated with a value of 2% of fuel consumption [10].

Results for mint cultivation and management, we derived a total consumption use of 16.7 GJ ha^-1 per year. Across all work phases, the harvest operation required the highest input (23.8%), while rolling and harrowing operations (carried out at the start of the vegetative cycle in the second and third years) resulted in the lowest value (0.8%). Soil preparation (fertilization, ploughing, and harrowing) represented 54.8% of the total energy input (Graph 1). The energy required for cultural operations (weed control) represented 8.3%. The energy analysis highlighted the high amount of direct energy consumed by fuel and lubricants (84% of total energy input).

Graph 1: Relative total energy by operation.

Economic aspects: Economic data were collected at the beginning of 2016 through personal interviews. All economic data (prices of outputs and inputs) refer to 2015 and to 1 ha, and output values refer to the essential oil produced from 1 ton of mint. The typical yield from 1 ha of mint ranges between 60 and 70 kg of raw essential oil. Output value is derived from the annual farmer-food producer contracted price, which is based on production cost. We collected the following data for each cultivation operation: inputs (fertilizer tonnes ha^-1); family labour or other labour (hours ha^-1); water (liters h-1; tractor and equipment utilization (hours ha^-1). To calculate the total cost of production, we divided the various components of cost into specific and corporate overhead. Cost types. Specific costs were composed of several annual operating costs: i) inputs; ii) operating machinery (tractors and equipment); iii) labour; iv) interest on operating capital; v) land. Corporate overheads comprised several groupings: i) farm insurance; ii) expenses for accounting; iii) share membership to Consortium of irrigation; iv) others [3,11-13].

Specific cost calculations are described below. Area farmers provided us fertilizers, herbicides, and irrigation water pricing information. Machinery costs were calculated on the basis of ‘hourly cost’ by machine type, and was then adjusted for depreciation, interest on machinery capital (“the present value of machinery by the rate of the capital borrowed to purchase it, or 4%” [11]), insurance (provided by farmers), maintenance (present value of machinery multiplied by 2%) to determine total cost [2,11]. Operating capital included the sum of annual input, labour, land rental (farmer provided), and machinery expenses specific to the mint crop, to which an operating capital cost was associated, represented by an interest expense of 6% per annum. Two sources of labour were considered that represented the only used on the farms considered in the study-family and temporary employees. Farmers provided temporary employee costs, while the cost of family labour was calculated according to the concept of opportunity cost with reference to the basic hourly wage of a ‘qualified horticultural worker’ [14]. Overhead cost estimates and calculations were based on information provided and reviewed by the farmers, and included distillation cost. Taxes were not included in the calculated production cost. Finally, total output minus total costs determined profit.

Table 1 shows the production cost of 1 ha of mint from Pancalieri for 2015. Specific costs account for approximately three-fourths of the total cost (74.18%), while the next highest cost portion is attributed to distillation at more than 22% of total cost. Overhead costs represent a mere 2.84% of total cost. Overall, the product is profitable.

Table 1: Production cost of mint of Pancalieri.

These early results show that the production of mint from Pancalieri is profitable. From an energy perspective, this crop seems to require little energy to produce, given the few and low energy input activities needed during its cultivation cycle. Note this study will be expanded to more farms to enhance its results. It has already benefited from the cooperation of Pancalieri operators and from previous research.

The authors express their sincere thanks to the farmers and Pancalieri operators that provided technical, economic data, and information that were instrumental to this work, and which has already benefited earlier research. A previous version of this work (poster) was presented at CIPAM 2016, 6th International Congress on Medicinal and Aromatic Plants during 29 May-1 June in Coimbra, Portugal.

The University of Torino funded this work with Local Research Funds from 2014 and 2015 under the scientific responsibility of Dr. Barbieri.

Manzone M is a co-author responsible for the work on energy consumption, while Barbieri C is author and responsible for the other parts of this document.