Perceptive preference toward recycling bin designs: Influential design item depending on waste type, the impact of past perception experiences on design preference, and the effect of color design on waste separation.

Efficient waste separation using recycling bins designed appropriately is promising for waste recycles. This study investigated recycling bin designs, in particular color and insert slot, and quantified perceptive preferences toward designs. This study hypothesized that design preference toward recycling bins is affected by past perceptions of recycling bin designs. Design categorization survey for 240 recycling bins used in public spaces shows that popular colors depend on design items and waste types. This study found that highly preferred colors were consistent with frequently used colors in certain design items, which was slot frame color for combustible and incombustible waste bins, and body color for PET bottle bins. Color preferences had statistically significant correlations with color usage rates (p = 0.009 for combustible waste bin, p = 0.032 for incombustible waste bin, and p = 0.012 for PET bottle bin, respectively). Although insert slot shape had moderate but significant correlations between slot shape preference and usage rate of slot shape (p = 0.002 or less for all recycling bins), the preference was mainly affected by slot largeness for combustible and incombustible waste bins. According to these results, this study concludes that the hypothesis was supported in particular for color preference. On the other hand, on-site experiments showed that the effect of only "impressive" color was too weak to improve waste separation. To encourage waste sorting using well-designed recycling bins, combination of preferred design items is necessary. Intensive usage of well-designed recycling bins for frequent perception opportunities is recommended as an environmental feedback to support sufficient design preference.

The effect of recycling bin design on PET bottle collection performance.

Many municipalities in Japan have collected PET bottles as recyclable waste since 1980s. When caps are removed from bottles, it reduces collection and transportation costs because bottles can be easily compressed by collection trucks. However, PET bottles collected from recycling bins are usually capped and include other materials. This study designed 10 recycling bins for PET bottle to investigate the effect of design on cap removal efficiency and recycling contamination (foreign waste mixture). Recycling bins for PET bottle were designed focusing on four design items. They are (1) individual recycling bins specifically for bottles and caps or all-in-one recycling bin for both bottle and cap collections, (2) inside-visibility (see-through), (3) signage (wording like "Bottle" and "Cap") near insert slot and (4) insert slot shape. PET bottle collection performance of designed recycling bins was monitored in Suzukakedai campus of Tokyo Tech. Perceptive preferences of recycling bin designs and insert slot shapes were measured by online surveys. Experimental results indicate that insert slot with round shape contributed to significantly lower recycling contamination than bottle-like shape although perceptive preference of insert slots with bottle-like shape was higher than that of the round shape. Signage and all-in-one design is significantly effective to promote cap removal only when it was set with other recycling bins. On the other hand, signage is effective to decrease recycling contamination in a single setting. This study found that design effect depended on the setting condition of recycling bins in terms of cap removal and foreign waste disposal.

The effects of setting conditions of trash bins on waste collection performance and waste separation behaviors; distance from walking path, separated setting, and arrangements.

This study investigated the effects of setting conditions of trash bins on waste collection, separation efficiency, and incorrect disposal. Tested trash bins are for combustible wastes, PET bottles, cans, and glass bottles. Monitoring results were analyzed by statistical tests to distinguish real effects and experimental errors. The distance to trash bins along walking path gave no significant effects on waste collection and the others. On the other hand, when the distance was out of walking path, its increase significantly decreased waste collection of combustible wastes. In contrast, the distance gave no significant effect on separation efficiency and foreign waste percentage. It was suggested that threshold distance that affects waste disposal behaviors is between 8 and 410 m. When trash bins were set separately, it affected the motivation of waste separations. Separated setting of combustible waste and PET bottle trash bins in the opposite side of the original position significantly decreased separation efficiencies of these wastes. Because no significant effect was found on separation efficiency of other wastes whose trash bins were set in the original position, additional 3 m distance to the opposite side might exceed the threshold distance and have caused low separation efficiencies. The preference of trash bin arrangement gave no significant effect on waste collection and the others excluding separation efficiency of can. These results suggest that appropriate location of trash bins can improve waste collection and waste separation. It might be useful for waste management in public areas with high population density like shopping mall.