The process also can sequester carbon and greenhouse gases otherwise released into the atmosphere from manure decomposition in lagoons.

“The conversion process reforms the organic matter in swine manure into oil with heat and pressure in an anoxic [devoid of oxygen], aqueous environment,” the authors say. “The product oil consists of mainly asphaltenes and resins. The specific gravity is around 1.01 (similar to that of petroleum asphalt binder, 1.03) with a boiling point of 300 degrees C and sulfur content of about 0.6 percent.”

As the chemical composition of bio-oil from swine manure is similar to that of petroleum, it is a promising candidate for the production of a bio-binder to be used in asphalt pavement, Fini, Kalberer and Shahbazi write. “To produce a bio-binder for use in asphalt pavement and as a crack sealant, the material should be engineered with the specific rheological and interfacial properties that are desirable for each application,” they state.

For instance, adhesives used in pavements and crack sealers require adequate creep and relaxation characteristics (to release stresses developed due to thermal and traffic loading) to be able to resist cracking, they say. In addition, because asphalt pavements are exposed to varied and extreme environmental conditions, a bio-binder’s resistance to aging and oxidation – as well as the corresponding temperature sensitivity and water susceptibility – will affect its performance.

Their paper presents the chemical and rheological characteristics of a biobinder and compares them with a typical bituminous binder. The authors found that the use of bio-binder from swine manure as a partial replacement for liquid-petroleum asphalt would enhance the asphalt binder’s rheological properties to provide better performance.

“Application of bio-binder in an asphalt mixture can allow for reduced mixing and compaction temperatures and enhanced workability,” they say. “This reduces fuel consumption and resultant CO2 emissions during plant production and pavement placement. Furthermore, bio-binder could enhance mixture workability to facilitate the production of high-RAP (reclaimed asphalt pavement) mixtures at lower temperatures with [warm mix asphalt] technologies.”

Use of this bio-binder should also reduce the cost of pavement construction due to its relatively low cost (50 cents per gallon), and reduce carbon emissions related to land application and storage of manure, they conclude. “Furthermore, it will minimize the pollution caused by odor and spillage from manure storage lagoons through reduced need for manure disposal,” they write. “Lastly, it provides potential sources of additional income for farmers through reducing the risk of unexpected spillage from lagoons, from marketing of the bio-binder, additional nutrient value in fertilizer, and potential carbon credits.”

Cold-in-Place Recycling Performance Benefits from Strong Foundation

Counter-intuitively, performance of cold-in-place recycled (CIR) pavements in New York State appears to be longest for highways carrying heavy traffic loads, compared to the low-volume rural roads it’s typically used for, say Warren H. Chesner, Ph.D., P.E., Christopher W. Stein, Henry G. Justus and Edward R. Kearney, Chesner Engineering, P.C., Long Beach, N.Y.; and Stephen A. Cross, Ph.D., P.E., professor, School of Civil and Environmental Engineering, Oklahoma State University-Stillwater, in their paper, Evaluation of Factors Affecting the Long Term Performance of Cold In-Place Recycled Pavements in New York State.

As described two months ago in these pages (see Hot, Cold and Green (and the 3Es), February 2011, pp. 20-29 or on our website at www.betterroads.com), cold-in-place recycling is an onsite recycling process in which an asphalt pavement with structural failures is reconstructed using 100-percent RAP to a typical treatment depth of 2 to 6 inches, using a mobile train of equipment that may include tanker trucks, a milling machine, crushing and screening equipment, a mixer, binder rejuvenating additives and a paver.

With CIR, existing pavement materials are removed, crushed, sized (if needed) and rejuvenated with a recycling agent. Its benefits include major pavement structural improvement via overhaul of the existing pavement materials, and CIR can cure most types of pavement distress. As with hot-in-place recycling, material hauling costs are minimized, while the blue smoke associated with HIR is eliminated.

“Foamed” or “expanded” asphalt is a type of CIR recycle or full-depth reclamation – depending on depth – in which hot performance-grade asphalt is foamed with water and air, and is injected into reclaimed materials and aggregate in a mixing chamber of a mobile unit or stationary plant, and offers a cost-effective option for FDR.

“In New York State, cold-in-place recycling (CIPR used by authors) is one of a series of asphalt pavement rehabilitation options designed to extend the service life of pavements,” the authors write. “Recycling pavements using CIPR has the potential to decrease energy consumption, and reduce the environmental burden and cost associated with asphalt pavement rehabilitation.”

However, one of the drawbacks to increased CIPR usage has been uncertainty about expected service life and factors that affect long-term CIPR performance, they say. “These uncertainties generally limit the use of CIPR to low-volume pavements to minimize the exposure of CIPR-rehabilitated pavements to aggressive traffic conditions,” they add. Thus they studied the effect of daily traffic, truck traffic, base thickness, base plus subbase thickness (total pavement thickness), geographical pavement location (environment and climate) and the condition of the pavement prior to CIPR rehabilitation on service life of CIPR pavements in New York State.

Data used in the analysis were compiled from the 2008 New York State DOT Pavement Management Group Highway Sufficiency Ratings Database, which represented 163 CIPR projects covering a pavement distance of 756 miles.