Reliable national data on waste generation and composition that will inform effective planning on waste management in Ghana is absent. To help obtain this data on a regional basis, selected households in each region were recruited to obtain data on rate of waste generation, physical composition of waste, sorting and separation efficiency and per capita of waste. Results show that rate of waste generation in Ghana was 0.47 kg/person/day, which translates into about 12,710 tons of waste per day per the current population of 27,043,093. Nationally, biodegradable waste (organics and papers) was 0.318 kg/person/day and non-biodegradable or recyclables (metals, glass, textiles, leather and rubbers) was 0.096 kg/person/day. Inert and miscellaneous waste was 0.055 kg/person/day. The average household waste generation rate among the metropolitan cities, except Tamale, was high, 0.72 kg/person/day. Metropolises generated higher waste (average 0.63 kg/person/day) than the municipalities (0.40 kg/person/day) and the least in the districts (0.28 kg/person/day) which are less developed. The waste generation rate also varied across geographical locations, the coastal and forest zones generated higher waste than the northern savanna zone. Waste composition was 61% organics, 14% plastics, 6% inert, 5% miscellaneous, 5% paper, 3% metals, 3% glass, 1% leather and rubber, and 1% textiles. However, organics and plastics, the two major fractions of the household waste varied considerably across the geographical areas. In the coastal zone, the organic waste fraction was highest but decreased through the forest zone towards the northern savanna. However, through the same zones towards the north, plastic waste rather increased in percentage fraction. Households did separate their waste effectively averaging 80%. However, in terms of separating into the bin marked biodegradables, 84% effectiveness was obtained whiles 76% effectiveness for sorting into the bin labeled other waste was achieved.

Sweet sorghum is an attractive feedstock for ethanol production. The juice extracted from the fresh stem is composed of sucrose, glucose, and fructose and can therefore be readily fermented to alcohol. The solid fraction left behind, the so-called bagasse, is a lignocellulosic residue which can also be processed to ethanol. The objective of our work was to test sweet sorghum, the whole crop, as a potential raw material of ethanol production, i.e., both the extracted sugar juice and the residual bagasse were tested. The juice was investigated at different harvesting dates for sugar content. Fermentability of juices extracted from the stem with and without leaves was compared. Sweet sorghum bagasse was steam-pretreated using various pretreatment conditions (temperatures and residence times). Efficiency of pretreatments was characterized by the degree of cellulose hydrolysis of the whole pretreated slurry and the separated fiber fraction. Two settings of the studied conditions (190 degrees C, 10 min and 200 degrees C, 5 min) were found to be efficient to reach conversion of 85-90%.

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The potential of wheat straw for ethanol production after pretreatment with O(3) generated in a plasma at atmospheric pressure and room temperature followed by fermentation was investigated. We found that cellulose and hemicellulose remained unaltered after ozonisation and a subsequent washing step, while lignin was degraded up to 95% by O(3). The loss of biomass after washing could be explained by the amount of lignin degraded. The washing water of pretreated samples (0-7 h) was analyzed for potential fermentation inhibitors. Approximately 30 lignin degradation products and a number of simple carboxylic acids and phenolic compounds were found, e.g., vanillic acid, acetic acid, and formic acid. Some components had the highest concentration at the beginning of the ozonisation process (0.5, 1 h), e.g., 4-hydroxybenzladehyde, while the concentration of others increased during the entire pretreatment (0-7 h), e.g., oxalic acid and acetovanillon. Interestingly, washing had no effect on the ethanol production with pretreatment times up to 1 h. Washing improved the glucose availability with pretreatment times of more than 2 h. One hour of ozonisation was found to be optimal for the use of washed and unwashed wheat straw for ethanol production (maximum ethanol yield, 52%). O(3) cost estimations were made for the production of ethanol at standard conditions.

BackgroundEnsiling is a well-known method for preserving green biomasses through anaerobic production of organic acids by lactic acid bacteria. In this study, wheat straw is subjected to ensiling in combination with hydrothermal treatment as a combined pretreatment method, taking advantage of the produced organic acids.ResultsEnsiling for 4 weeks was accomplished in a vacuum bag system after addition of an inoculum of Lactobacillus buchneri and 7% w/w xylose to wheat straw biomass at 35% final dry matter. Both glucan and xylan were preserved, and the DM loss after ensiling was less than 0.5%. When comparing hydrothermally treated wheat straw (170, 180 and 190°C) with hydrothermally treated ensiled wheat straw (same temperatures), several positive effects of ensiling were revealed. Glucan was up-concentrated in the solid fraction and the solubilisation of hemicellulose was significantly increased.Subsequent enzymatic hydrolysis of the solid fractions showed that ensiling significantly improved the effect of pretreatment, especially at the lower temperatures of 170 and 180°C.The overall glucose yields after pretreatments of ensiled wheat straw were higher than for non-ensiled wheat straw hydrothermally treated at 190°C, namely 74-81% of the theoretical maximum glucose in the raw material, which was ~1.8 times better than the corresponding yields for the non-ensiled straw pretreated at 170 or 180°C. The highest overall conversion of combined glucose and xylose was achieved for ensiled wheat straw hydrothermally treated at 180°C, with overall glucose yield of 78% and overall conversion yield of xylose of 87%.ConclusionsEnsiling of wheat straw is shown to be an effective pre-step to hydrothermal treatment, and can give rise to a welcomed decrease of process temperature in hydrothermal treatments, thereby potentially having a positive effect on large scale pretreatment costs.