Non-commensurable values of the pecan industry

By

J.G. Mexal, E.A. Herrera, T.D. Sammis , and W.H. Zachritz, II

New Mexico State University, Las Cruces, NM 88003

Introduction

The pecan industry in New Mexico and west Texas has grown tremendously since pecans were first introduced to the valley by NMSU in 1915. From that original four-acre planting, the industry has grown to over 17,000 ha with over 2,000,000 trees. Production in New Mexico peaked in 1999 at 23,000 Mg worth $48 million, while west Texas produced an additional 9,000 Mg. The yield of the year 2000 crop has been estimated at 14,000 Mg worth $42 million (Figure 1). However, the trend in increased planting of pecans and the relatively young age of many pecan trees indicates that the volume of production likely will continue to increase.

While the value of the pecan industry can easily be measured from a nut production standpoint, there are other, less obvious, benefits to the community. Hartman et al. (2000) identified the following benefits of trees to a community:

* supply oxygen * sequester carbon dioxide

* reduce noise pollution * trap particulates

* alter microclimate * improve aesthetics

* enhance outdoor urban spaces * alter the character of a community.

Obviously, the opportunity to provide income was not included. These benefits are difficult to quantify and even more difficult to attach a dollar value. Hence, the values are non-commensurable, since they do not have a common metric. The objective of this paper is to discuss the non-commensurable values of the pecan industry in New Mexico and west Texas in relation to the commensurable values.

Assumptions

For ease of calculation, we will assume that the 2 million pecan trees in the New Mexico/west Texas region are mature (at least 15 yrs old) with the following characteristics based on destructive harvest of four trees (Kraimer, unpubl):

Table 1. Estimated biomass partitioning of mature pecan trees (Kraimer, unpubl.).

Parameter	Trunk	Branches	Leaves	Husks	Pecans	Roots	Total
Kg/tree	263	541	64	10	28	362	1268
Kg/tree/yr	17	111	64	10	28	24	254

Thus, the model pecan orchard with 120 trees/ha produces 30,000 kg biomass/ha/yr with an annual nut production of 3,400 kg/ha/yr. Furthermore, we will assume no biennial bearing. These estimates will be used for our ‘target’ orchard when no other information is available or to estimate the production target.

Commensurable Values

Leaves and shucks In addition to shelled pecans, there are other potential sources of saleable products extracted from pecan orchards. During the harvesting process, the pecans are separated from dry leaves and shucks, which amounts to about 74 kg/tree or about 4,400 kg/ha/yr. Conceivably, this biomass could be harvested, mulched or composted and sold. However, this organic material has more potential value when left in the orchard and recycled in place.

Pecan shells The New Mexico/west Texas pecan industry produced about 32,000 Mg of in-shell pecans in 1999. At an average shell-out percentage of 55%, about 14,000 Mg of shells are produced each year. The model orchard produces 1,500 kg shells from 3,400 kg pecans or about 66,000 Mg of shells/yr. Thus, the region could product 14,000 to 66,000 Mg of shell/yr. This biomass could be used as a biofuel for a small power plant. The value would be about $20/ton or $280,000 to $520,000 additional value/yr. Alternatively, the material could be used in the horticultural industry as a mulch or potting medium. Generally, this use has a higher value than biofuel. At $50/m³for potting medium, pecan shells would have a value of $1,400,000 to $2,600,000 assuming 500 kg/m³.

Orchard prunings Every 2-3 years, the upper branches of mature orchards are pruned to reduce the height of trees and improve light penetration to the lower canopy. Generally, the orchards are pruned in the north-to-south direction only. The model orchard tree produces about 110 kg branch wood/tree/yr. Thus, annual branch wood production totals more than 13,000 kg/ha/yr. The upper canopy of the trees is pruned on two sides (east and west). Potentially, only ½ of the branch wood is pruned, and perhaps less than ¼, since only the upper canopy is pruned. Thus, perhaps 3,000 kg/ha/yr would be pruned, or about 52,000 Mg/yr in the region. At $20/Mg biofuel, the value of the prunings would be over $1,000,000/yr, providing fuel at the rate of 6 Mg/hr for power generation.

Converting pecan shells and orchard prunings into saleable products could increase the gross income of pecan growers by $1,400,000 to $2,500,000/yr.

Non-Commensurable Values

The eight non-commensurable values defined by Hartman et al. (2000) can be categorized into five general headings: carbon sequestration, oxygen release, pollution control, altered microclimate and beauty enhancement.

Carbon Sequestration Pecan orchards can serve as sinks for carbon dioxide, in spite of the fact that much of the carbon that would be fixed would eventually be consumed either as pecan kernels or biofuels. Plants remove carbon dioxide from the atmosphere and convert it to carbohydrates via the photosynthetic reaction, simplified below (Figure 1).

Thus, for every unit of carbohydrate created by the pecan tree, almost 1.5 units of carbon dioxide are removed from the atmosphere (Figure 1). Much of the fixed carbon dioxide will be respired back into the atmosphere either as consumed pecans or decomposed litter in the orchard, or burned biofuels. However, as much as 49% of the fixed CO₂ will remain in the tree. Using the model tree, approximately 125 kg would remain fixed. This equates to over 255,000 Mg/yr fixed by all the pecans in the region. Storing 255,000 Mg of carbohydrate as pecan wood removes 375,000 Mg CO₂ in the process. The CO₂ fixed by pecans was generated from fuel combustion in automobiles. Roughly, an automobile generates 0.25 kg CO₂/ km driven. Thus, the 375,000 Mg CO₂ is equivalent to 62,500 vehicles driving 24,000 km/yr.

Figure 1. Basic photosynthetic reaction and relative partitioning of fixed carbon.

Oxygen Release In addition to removing CO₂ from the atmosphere, the photosynthetic process also generates over 1 kg O₂ for every 1 kg CO₂ fixed. Consequently, storing 255,000 Mg of carbon in pecan wood releases over 270,000 Mg of O₂. This oxygen is then used by us in the air we breathe. Each human needs about 200 kg O₂/yr. The pecan orchards provide enough oxygen for nearly 1.4 million people in the New Mexico-Texas-Chihuahua region.

Pollution Control Trees are excellent screens that trap dust and other pollutants. One hectare of trees traps over 500 kg of pollutants, including over 200 kg of ozone and 150 kg of particulates. According to a study in California, each hectare of trees is worth over $5,600 in emission reduction credits (ERC). Thus, the 17,200 ha of pecans in NM/TX trap over 8,600 Mg of pollutants valued at nearly $96 million.

Another, less obvious form of pollution is noise pollution. Trees and shrubs planted between the home and source of the noise (e.g. highways) can reduce the noise level by nearly 10 decibels (Figure 2). A 10-decibel (dBA) reduction in noise is a 10-fold reduction in noise, analogous to the Richter scale for earthquakes.

Altered Microclimate Trees are important components of a residential landscape, especially in a hot, dry climate such as the southwest. Pecans are ideally suited as landscape trees in New Mexico. Pecans are one of the last trees to break but in the spring (early to mid-April), and one of the last to lose their leaves in the fall (late-October). Thus, they can provide shade for a residence when it is needed (May through October), and allow the sun to warm the home when air conditioning is not needed.

In addition to providing shade, trees can serve as both windbreaks and sound barriers for homeowners and livestock. A windbreak of trees and shrubs can decrease wind velocity on the leeward side by 40% to 80% compared to the windward side.

The benefits from shade, reduced cooling costs, and wind reduction can be substantial. McPherson and Rowntree (1993) determined the benefit of landscape trees in different environments. Each 25 foot tall tree planted around a home decreased home cooling costs as much as $30/yr (Figure 3). Thus, 4 trees could reduce utility expenses by up to $10/mo.

Figure 2. Noise reduction (dBA) by tree and shrub barrier near highway compared to no barrier (Miller 1988).

Figure 3. Energy savings accrued to a 25 ft tree planted near a home (McPherson and Rowntree 1993).

Enhanced Beauty The intrinsic beauty of trees in the landscape of a home or community is difficult to quantify. However, a reasonable estimate is trees increase the value of home by about 1%/yr. Thus, a $100,000 home that is 25 years old would have an additional worth of about $25,000 because of the mature landscaping.

Bottom Line

Pecans are extremely valuable not only to the producer in NM/west Tx, but also to the citizenry in general. The industry currently has an annual value approaching $50 million. The value will only grow as young orchard mature. However, other products could further increase the value of the pecan industry an additional 5% to 10% through the development of new industries.

While the pecan industry is economically important to the region, the non-commensurable value of pecan is enormously greater. The trees provide oxygen, sequester carbon dioxide, and buffer our personal environment against wind, rain and sun. Furthermore, the pecan orchards are a major attraction for visitors and residents alike.

Table 2. Summary of the benefits of pecans to New Mexico/west Texas.

Commodity	Commensurable Value	Non-commensurable Value
Pecans	$42.0 - $48.0 million
Shells	$ 0.3 - $ 2.6 million
Prunings	$ 1.4 - $ 2.5 million
Leaves & Shucks		Organic matter addition
Carbon Sequestration		62,500 vehicles
Oxygen Release		1.4 million people
Pollution Control		Emission reduction credits ($96 million)
Climate Modification		$30/tree
Beauty		1%/yr/home
Total Benefit	$43.7 - $53.1 million	Priceless

References

Hartman, J.R., T.P. Pirone, M.A. Sall. 2000. Pirone’s Tree Maintenance. 7^th ed. Oxford Univ. Press, NY, 545 p.

McPherson, E.G. and R.A. Rowntree. 1993. Energy conservation potential of urban tree planting. J. Arboriculture 19:321-331.

Miller, R.W. 1988. Urban Forestry. Planning and Managing Urban Greenspaces. Prentice Hall, Englewood Cliffs, NJ, 404 p.