Sustainable agriculture collectively is farming using least damaging techniques to provide food and energy for increasing population without compromising the ecosystem and the environment. Sustainable agriculture is one of the main loops of food security chain , Broadly speaking, approximately, more than thirty percent of produced food is being lost or wasted in total amount of food chain . Therefore, better knowledge to reduction of food waste is essential to provide a solution to the problem. Not only that AIBP enforces negative effect on the environment, human health and resources beside but also is a threat to the food security [3–7]. food production is responsible for 19–29% of global greenhouse gas emissions by is beside the resources impacts of food waste which assume as serious problem. In the recent decades, many studies have focused on the bioeconomy of treated agro-industrial by-products (AIBP) recycling and its bioconversion in the livestock. High nutrient content of AIBP makes it an ideal candidate as feedstuff. Bioeconomy is trying to promote the added value to AIBP thus introducing new marketplaces and technologies for the future. AIBP can be a substitute to traditional feedstuff such as grains or protein resources. Inclusion of AIBP as feedstuff has positively affected the animal while reducing the agricultural wastes as the environmental contaminators.
A natural barrier and concern for applicability of AIBP regarding livestock feed is its high problematic moisture content and presence of contaminants. According to literature there is a lack of data on the digestibility of food waste in livestock nutrition.
Studying AIBP as feedstuff sources provide insights into the methods for reduction of cost of formulation of feed, milk and beef production. Although ruminants can be assumed as a huge biorefineries of agro-industrial by-products, but it is well established that farmed ruminants are responsible for a substantial amount of anthropogenic methane emissions worldwide . Microbial consortium including archaea, bacteria, protozoa and fungi living in the rumen, can convert vast amount of bio polymers by their enzymatic systems in to volatile fatty acids (VFA) and microbial protein that can be used by the ruminants for maintenance, growth and production . Beside VFA production, molecular hydrogen (H2), carbon dioxide (CO2) and some other gases are also produced. In the rumen, as an anerobic chamber, microbial consortium can produce methane (CH4) by using H2 for reducing CO2 into methane (CH4) [6, 11–14].
Ruminants due to their rumen microbial consortium can use AIBP to meet their requirements of growth, reproduction and production. Utilizing locally available AIBP beside ruminant’s potential seems a practical alternative.
Sugar beet pulp (SBP) Apple pomace (AP) Orange pulp (OP) are three agro-industrial by-products as potential alternative feedstuff. Also, replacing this AIBP with a part of a conventional diet ingredient due to its energy and protein not only contribute to environmental contamination cut but also develop bio-economy by bio-recycling of these AIBPs. Handful studies have investigated the use of apple pomace silage in ruminant diets [15, 16].The results of a study showed that feeding dairy cows with apple pomace silage containing 10% wheat straw, 10% alfalfa hay, and 10% rice hulls resulted in an increase in milk yield and milk protein content. Another study revealed that apple pomace silage could be added to the diet of lactating cows up to 30% . However, the combination of apple pomace silage and other types of silage has not been studied adequately . Other agro-industrial by-products could also be used as a feedstuff (e.g., apple pomace and orange pulp, by-products of juice extraction industry). These products with high fermentable nutrients used whether as fresh, dry, or ensiled can be effectively fermented by ruminal microorganisms [20–24]. Per report of Paya et al. (2012) nutritive values of dry apple pomace (DAP) and dry orange pulp (DOP) were; crude protein (CP): 7.2% − 7.9%, ether extract (EE): 2.9%- 1.8%, neutral-detergent fiber (NDF):43.3% − 22.4%, acid detergent fiber (ADF): 32.3% − 15.3% and metabolizable energy (ME): 10.8–8.3 MJ/Kg, These values represent suitable capacity of these processed wastes as feedstuff which is not in competing with human food. Not only the nutritive value, but also economically being suitable as an alternative for feedstuff make these agro-industrial by-products useful [19, 25]. The hypothesis that we followed in the present study was that; biorefining of agro-industrial by-products can decrease environmental contaminators beside producing the food for human.
Additional investigation of AIBP would further our understanding on behavior and pattern of AIBP as a source of non-fiber carbohydrates on degradation and biogas kinetics, methane emission and in vitro fermentation parameters.