Energy use and nutrient cycling in pig production systems

Project Overview

Project Type: Graduate Student
Funds awarded in 2007: $9,969.00
Projected End Date: 12/31/2009
Grant Recipient: Iowa State University
Region: North Central
State: Iowa
Graduate Student:
Faculty Advisor:
Mark Honeyman
Iowa State University

Annual Reports


  • Animals: swine


  • Animal Production: general animal production
  • Energy: energy conservation/efficiency, energy use


    This project quantified the energy use in the construction and operation of different types of pig production systems in Iowa. In general producing pigs in Iowa in 2009 requires nearly 85% less non-renewable energy compared to 1975. Using bedded hoop barns for gestating sows and grow finish pigs requires less energy to heat and ventilate buildings but more energy to grow and process feed than conventional systems. The total energy used for both housing systems is very similar. Energy use for pig production is influenced by crop sequence and diet strategy with nitrogen management being the major leverage point.


    United States pig production is concentrated in the North Central Region, and is a major influence on the economic and ecological well-being of that community. Although often viewed as isolated entities at a macro-level, production of both crops and livestock are heavily influenced by each other. Recognizing influences between crops and livestock, and particularly utilizing complementary aspects of pig production and cropping systems is essential for achievement of greater sustainability within the North Central United States.

    Energy is used in all aspects of pig production, from the manufacture of materials used in building construction to the cultivation and processing of feedstuffs. Historically the availability of fossil fuels has minimized pressure to critically consider all uses of energy in pig production. Interest in non-solar energy use for all sectors of society is increasing due to rising energy prices, uncertainty about access to fossil fuel reserves, and growing consensus about the deleterious implications fossil fuel use has for global climate. Comprehensive, accurate information is critical to informed decision making. However analysis of energy use by modern pig farms in Iowa, the region, and United States is lacking.

    Life cycle assessment (LCA) is a technique used to quantify and compare environmental impacts of products or processes. Although most commonly applied to manufacturing processes, LCA is increasingly being applied to agriculture. Previous LCA’s of swine production have focused on European systems, particularly Denmark (Halberg, 1999; Zhu and van Ierland, 2004; Basset-Mens and van der Werf, 2005; Ericksson et al., 2005; Williams et al., 2006; Dalgaard et al., 2007; Meul et al., 2007). There are fundamental differences between European and United States swine production that limits the application of European results to inform decision making by pig producers in the United States. European swine diets typically include more variety of feed ingredients and often include high amounts of small grains such as barley. Peas, rapeseed cake, and soybean meal are all commonly used as protein sources in European swine diets. In the United States, swine diets are almost entirely comprised of corn and soybean meal. Growing pigs are usually limit fed in Europe but fed ad libitum in the United States. Feeding pelleted or liquid feeds is Europe is common while in the United States almost all diets are ground and fed dry. Some US farms provide water at the feeder, encouraging consumption of a wet-dry feed, but this strategy is very different from liquid feeding systems seen in Europe. Finally climate conditions and primary environmental concerns differ between Europe and the United States.

    Broadly, a pig production system consists of three features: the buildings used to house pigs, the diets fed the animals, and the cropland used to produce the feedstuffs. The purpose of this project is to examine non-solar energy use of different facility type × crop sequence × diet formulation strategies. Greenhouse gas emissions are also estimated based on non-solar energy use.

    Conventional farrow-to-finish swine facilities in Iowa are mechanically ventilated buildings with liquid manure handling systems. Pigs are born in farrowing crates and at weaning are moved to a heated nursery facility. As pigs grow, they are moved from nursery facilities to larger grow-finish buildings. Grow-finish buildings typically house 1,200 animals in pens of 30-60 animals. The entire floor space is slatted concrete. Gestation occurs in buildings similar to grow-finish buildings except pens are replaced with individual gestation stalls. Conventional housing for swine in Iowa and a hoop barn-based alternative have been detailed and examined (Lammers et al., 2009b; Lammers et al., 2009c). The hoop barn-based alternative uses similar farrowing and nursery facilities as the conventional system, but grow-finish pigs and gestating sows are housed in bedded hoop barns. Hoop barns in Iowa are 21.9 × 9.1 m QuonsetTM- shaped structures that have been previously described (Honeyman et al., 2001; Brumm et al., 2004; Harmon et al., 2004). Hoop barn sidewalls are approximately 1.5 m high and consist of wooden posts and sidewalls. Tubular steel arches are attached to the posts, forming a hooped roof. An ultraviolet light resistant, high-density polyethelyne tarp is pulled over the arches and fastened to the sidewalls. The floor is solid, usually concrete, with raised areas for eating and drinking. The rest of the floor is bedded with corn stalks or other plant materials. Buildings for grow-finish pigs are managed as a single pen with 180–200 animals per pen (Honeyman et al., 2001; Honeyman and Harmon, 2003). Gestating sows in hoop barns are managed in group pens with individual feeding stalls (Lammers et al., 2007; Lammers et al., 2008a).

    The most common crop sequence in Iowa is a corn-soybean rotation. This sequence is highly productive in terms of starch and amino acids produced, but is heavily reliant on fossil fuels to provide fertility and has been associated with a number of undesirable ecological impacts. For this analysis, an alternative of corn-soybean-corn-oat under-seeded with a leguminous cover crop was examined.

    Two diet formulation strategies are also considered. The first formulation strategy (SIMPLE) does not include synthetic amino acids or phytase. The second (COMPLEX) reduces crude protein content of the diet by using L-lysine to meet SID lysine requirements of pigs and includes the exogenous enzyme phytase. Use of synthetic amino acids and exogenous phytase is common practice in modern pig production based on economics and environmental regulation. The industrial processes for manufacturing L-lysine and exogenous phytase is energy intensive. The two formulation strategies were selected in order to evaluate the systemic effectiveness of substituting synthetic amino acids and exogenous enzymes for more basic feed ingredients in terms of non-solar energy use.

    This project summarizes the non-solar energy use of pig production systems in Iowa. The baseline system—pigs housed in conventional confinement facilities and fed complex corn-soybean meal diets produced on land cultivated in a corn-soybean sequence—is representative of how the majority of pigs in the Midwest United States are produced. Selected combinations of facility type × crop sequence × diet formulation strategies were compared to the baseline system. Greenhouse gas emissions are also estimated based on non-solar energy use. This project provides a current analysis of modern pig production systems and identifies leverage points for minimizing non-solar energy use and associated greenhouse gas emissions by pig production systems.

    Project objectives:

    Three expected outcomes were identified in the proposal of this research project for the short, intermediate, and long term. They are as follows:
    1. Short term: quantification of energy use in pig production systems.
    2. Intermediate term: objectively evaluate energy use choices and alternatives in pig production systems.
    3. Long term: practice and policy enhancing the sustainability of the region and nation.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.