One of the main reasons for the continued increase in the deficit of affordable housing in Nigeria is the high cost of brick made from sand and ordinary Portland cement (OPC). Finding a replacement for cement to assure sustainability is crucial as the raw materials used in making cements which are naturally occurring are depleting. Rice husk was milled and sieved to reduce the size to 0.020 mm. The moisture content of the rice husk was 9.98%, bulk density was 609.61g cm -3 and the ash content was 18.74%. Rice husk was wetted for 3, 6, 9, 12, 15 and 21 h and mixed with slaked lime at the ratios of 1:1, 3:1, 2:3 and 3:2. The composite was molded in cylindrical and rectangular mold using mechanical and hydraulic press. The compressive strength (CS) (N/mm 2 ) was tested at ages of 7, 14 and 21 days. The results show higher compressive strength in 1:1 as the bricks ages and also greater strength when wetted for 15 h. For 15 h wetting, 1:1 had CS (N/mm 2 ) of 2.59, 6.07 and 11.23. If well optimized, rice husk can be an excellent material for brick production thereby presenting a good alternative to OPC.

The pulp and paper industry is the sixth largest polluter discharging a variety of gaseous, liquid and solid wastes into the environment. This pollution mainly arises due to chemicals used during production, so this study compared these two chemicals to determine the better one for a cleaner production process. A dewatered kenaf stem was cooked in the 20, 60 and 90% concentrations of formic acid and sodium hydroxide at time intervals of 1, 2 and 3 h to compare the solids (total suspended solid, total dissolved solid and total solid) of their effluent for environmental friendliness. After examining the whole concentrations and the time intervals, 60% concentration of the acids at 2 h pulping gave better pulp on physical examination. When the solids of the effluents of the two chemicals were analyzed, formic acid effluent had a TSS of 5768 mg/L, TDS of 54088 mg/L and TS of 59855 mg/L, while that of sodium hydroxide was 6053 mg/L for TSS, 96628 mg/L for TDS and 102680 mg/L for TS. This study showed that pulping of kenaf stem with 60% formic acid for 2 h has effluent that is greener than the use of sodium hydroxide of the same concentration at the same duration.

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Pulp and paper production process releases different types of wastes into the environment and pulp mill sludge is one of the major wastes from pulp and paper mill. The environmental awareness has led to more attention being given to the process of paper production and the raw materials and chemical usage. In this study, we analyzed the effect of chemical, concentration and cooking time on the characteristics of sludge and physical appearance of pulp obtained from pulping kenaf stem. The stem was pulped with 20%, 60% and 90% concentrations of formic acid and sodium hydroxide at 1 hour, 2 hours and 3 hours intervals to determine the parameters of their sludge as well as pulp appearance. The parameters considered include carbon, nitrogen, turbidity, phosphorus, ash and moisture. Sludge from sodium hydroxide pulping showed lowest value (0.02) of carbon with 60% concentration and highest (4.30) with 90% after 1hr cooking. Formic acid sludge that reported zero carbon with 20% concentration gave lowest value (1.77) at 60% after 1hr and highest value (8.73) after 3hrs with 90% concentration. Both formic acid and sodium hydroxide sludge recorded highest values (0.29 & 39.77) of nitrogen at 60% concentrations. The sludges of the two chemicals were most turbid at 90% and less at 60% concentrations with highest phosphorus values at the same concentrations. Both sludges reported lowest moisture contents at 60%. Sodium hydroxide showed highest ash at 20% after 1hr cooking while the highest value for formic acid was recorded at 90% after 3hrs cooking. The 60% formic acid at 2 hours gave a better pulp on physical examination and the sludge from the same process can also be reused.

The pulp and paper industry is considered as one of the major potential sources of pollution in the environment and a consumer of wood. Environmental effects have been attributed to chemicals introduced during the manufacturing process. This paper investigated the influence of cooking chemicals, concentration and time on the properties of effluent generated during pulping of agricultural residue. A stem of kenaf which is an agricultural residue was pulped with 20%, 60% and 90% concentrations of formic acid and sodium hydroxide at 1 hour, 2 hours and 3 hours intervals to determine the characteristics of their effluents. The lowest Chemical Oxygen Demand (COD) obtained from formic acid effluent for the 3 hours cooking at 20%, 60% and 90% concentrations was 324mg/l at 60% concentration after cooking for 2 hours while sodium hydroxide effluent has 3050mg/l at 20% concentration after 1hour cooking as its lowest. Formic acid effluent showed lowest Biological Oxygen Demand (BOD) of 10.63mg/l at 60% concentration after cooking for 2 hours while sodium hydroxide has 13.75mg/l at 90% after 1 hour cooking. The value of Total Solid (TS) from formic acid effluent was lowest (16890mg/l) at 60% concentration after cooking for 2 hours while sodium hydroxide lowest value (15524mg/l) was recorded at 20% after 3 hours cooking. Sodium hydroxide effluent has lowest Total Suspended Solid (TSS) of 3165mg/l while formic acid has 2245mg/l both at 90% concentrations after 2 and 3 hours cooking.